diff --git a/auto_tests/TCP_test.c b/auto_tests/TCP_test.c
index ca5afd9a..8e75fae0 100644
--- a/auto_tests/TCP_test.c
+++ b/auto_tests/TCP_test.c
@@ -294,7 +294,7 @@ END_TEST
 static int response_callback_good;
 static uint8_t response_callback_connection_id;
 static uint8_t response_callback_public_key[crypto_box_PUBLICKEYBYTES];
-static int response_callback(void *object, uint8_t connection_id, uint8_t *public_key)
+static int response_callback(void *object, uint8_t connection_id, const uint8_t *public_key)
 {
     if (set_tcp_connection_number(object - 2, connection_id, 7) != 0)
         return 1;
@@ -321,7 +321,7 @@ static int status_callback(void *object, uint32_t number, uint8_t connection_id,
     return 0;
 }
 static int data_callback_good;
-static int data_callback(void *object, uint32_t number, uint8_t connection_id, uint8_t *data, uint16_t length)
+static int data_callback(void *object, uint32_t number, uint8_t connection_id, const uint8_t *data, uint16_t length)
 {
     if (object != (void *)3)
         return 1;
@@ -342,7 +342,7 @@ static int data_callback(void *object, uint32_t number, uint8_t connection_id, u
 
 static int oob_data_callback_good;
 static uint8_t oob_pubkey[crypto_box_PUBLICKEYBYTES];
-static int oob_data_callback(void *object, uint8_t *public_key, uint8_t *data, uint16_t length)
+static int oob_data_callback(void *object, const uint8_t *public_key, const uint8_t *data, uint16_t length)
 {
     if (object != (void *)4)
         return 1;
diff --git a/auto_tests/tox_test.c b/auto_tests/tox_test.c
index f8da8560..1a3c5868 100644
--- a/auto_tests/tox_test.c
+++ b/auto_tests/tox_test.c
@@ -30,7 +30,7 @@ void accept_friend_request(Tox *m, const uint8_t *public_key, const uint8_t *dat
 }
 uint32_t messages_received;
 
-void print_message(Tox *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_message(Tox *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     if (*((uint32_t *)userdata) != 974536)
         return;
@@ -44,7 +44,7 @@ void print_message(Tox *m, int friendnumber, uint8_t *string, uint16_t length, v
 
 uint32_t name_changes;
 
-void print_nickchange(Tox *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_nickchange(Tox *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     if (*((uint32_t *)userdata) != 974536)
         return;
@@ -69,7 +69,7 @@ void print_typingchange(Tox *m, int friendnumber, uint8_t typing, void *userdata
 uint8_t filenum;
 uint32_t file_accepted;
 uint64_t file_size;
-void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename,
+void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, const uint8_t *filename,
                          uint16_t filename_length, void *userdata)
 {
     if (*((uint32_t *)userdata) != 974536)
@@ -85,7 +85,7 @@ void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t
 uint32_t file_sent;
 uint32_t sendf_ok;
 void file_print_control(Tox *m, int friendnumber, uint8_t send_recieve, uint8_t filenumber, uint8_t control_type,
-                        uint8_t *data, uint16_t length, void *userdata)
+                        const uint8_t *data, uint16_t length, void *userdata)
 {
     if (*((uint32_t *)userdata) != 974536)
         return;
@@ -100,7 +100,7 @@ void file_print_control(Tox *m, int friendnumber, uint8_t send_recieve, uint8_t
 
 uint64_t size_recv;
 uint8_t num;
-void write_file(Tox *m, int friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
+void write_file(Tox *m, int friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length, void *userdata)
 {
     if (*((uint32_t *)userdata) != 974536)
         return;
diff --git a/docs/TODO b/docs/TODO
index fc50d566..966a1b5f 100644
--- a/docs/TODO
+++ b/docs/TODO
@@ -24,8 +24,8 @@ Lossless UDP:
     [DONE] Call initiation
     [DONE] Encryption
     [IN PROGRESS] Auditing.
-    [NOT STARTED] Video packet splitting.
-    [NOT STARTED] Prevent audio skew.
+    [NEEDS TESTING] Video packet splitting.
+    [IN PROGRESS] Prevent audio skew (seems to be easily solvable client side.)
     [IN PROGRESS] Group chats.
 
 Friend_requests.c:
diff --git a/testing/Messenger_test.c b/testing/Messenger_test.c
index 7c1d64e7..905bcef4 100644
--- a/testing/Messenger_test.c
+++ b/testing/Messenger_test.c
@@ -56,7 +56,7 @@
 
 #endif
 
-void print_message(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_message(Messenger *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     printf("Message with length %u received from %u: %s \n", length, friendnumber, string);
     m_sendmessage(m, friendnumber, (uint8_t *)"Test1", 6);
diff --git a/testing/nTox.c b/testing/nTox.c
index 050ec93d..971a2571 100644
--- a/testing/nTox.c
+++ b/testing/nTox.c
@@ -876,14 +876,16 @@ void print_request(Tox *m, const uint8_t *public_key, const uint8_t *data, uint1
     do_refresh();
 }
 
-void print_message(Tox *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_message(Tox *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     /* ensure null termination */
-    string[length - 1] = 0;
-    print_formatted_message(m, (char *)string, friendnumber, 0);
+    uint8_t null_string[length + 1];
+    memcpy(null_string, string, length);
+    null_string[length] = 0;
+    print_formatted_message(m, (char *)null_string, friendnumber, 0);
 }
 
-void print_nickchange(Tox *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_nickchange(Tox *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     char name[TOX_MAX_NAME_LENGTH + 1];
 
@@ -899,7 +901,7 @@ void print_nickchange(Tox *m, int friendnumber, uint8_t *string, uint16_t length
     }
 }
 
-void print_statuschange(Tox *m, int friendnumber, uint8_t *string, uint16_t length, void *userdata)
+void print_statuschange(Tox *m, int friendnumber, const uint8_t *string, uint16_t length, void *userdata)
 {
     char name[TOX_MAX_NAME_LENGTH + 1];
 
@@ -999,7 +1001,7 @@ void print_help(char *prog_name)
     puts("  -f keyfile      [Optional] Specify a keyfile to read from and write to.");
 }
 
-void print_invite(Tox *m, int friendnumber, uint8_t *group_public_key, void *userdata)
+void print_invite(Tox *m, int friendnumber, const uint8_t *group_public_key, void *userdata)
 {
     char msg[256];
     sprintf(msg, "[i] received group chat invite from: %u, auto accepting and joining. group number: %u", friendnumber,
@@ -1055,7 +1057,8 @@ void print_groupchatpeers(Tox *m, int groupnumber)
     new_lines_mark(msg, 1);
 }
 
-void print_groupmessage(Tox *m, int groupnumber, int peernumber, uint8_t *message, uint16_t length, void *userdata)
+void print_groupmessage(Tox *m, int groupnumber, int peernumber, const uint8_t *message, uint16_t length,
+                        void *userdata)
 {
     char msg[256 + length];
     uint8_t name[TOX_MAX_NAME_LENGTH] = {0};
@@ -1116,7 +1119,7 @@ void print_groupnamelistchange(Tox *m, int groupnumber, int peernumber, uint8_t
         print_groupchatpeers(m, groupnumber);
     }
 }
-void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename,
+void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, const uint8_t *filename,
                          uint16_t filename_length, void *userdata)
 {
     char msg[512];
@@ -1131,8 +1134,7 @@ void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t
 }
 
 void file_print_control(Tox *m, int friendnumber, uint8_t send_recieve, uint8_t filenumber, uint8_t control_type,
-                        uint8_t *data,
-                        uint16_t length, void *userdata)
+                        const uint8_t *data, uint16_t length, void *userdata)
 {
     char msg[512] = {0};
 
@@ -1146,7 +1148,7 @@ void file_print_control(Tox *m, int friendnumber, uint8_t send_recieve, uint8_t
     new_lines(msg);
 }
 
-void write_file(Tox *m, int friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
+void write_file(Tox *m, int friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length, void *userdata)
 {
     char filename[256];
     sprintf(filename, "%u.%u.bin", friendnumber, filenumber);
diff --git a/testing/tox_sync.c b/testing/tox_sync.c
index 68cad9f4..523f2c56 100644
--- a/testing/tox_sync.c
+++ b/testing/tox_sync.c
@@ -130,7 +130,7 @@ int not_sending()
 
 static char path[1024];
 
-void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename,
+void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t filesize, const uint8_t *filename,
                          uint16_t filename_length, void *userdata)
 {
     char fullpath[1024];
@@ -169,7 +169,7 @@ void file_request_accept(Tox *m, int friendnumber, uint8_t filenumber, uint64_t
 }
 
 void file_print_control(Tox *m, int friendnumber, uint8_t recieve_send, uint8_t filenumber, uint8_t control_type,
-                        uint8_t *data,
+                        const uint8_t *data,
                         uint16_t length, void *userdata)
 {
     if (recieve_send == 1 && (control_type == TOX_FILECONTROL_KILL || control_type == TOX_FILECONTROL_FINISHED)) {
@@ -185,7 +185,7 @@ void file_print_control(Tox *m, int friendnumber, uint8_t recieve_send, uint8_t
     }
 }
 
-void write_file(Tox *m, int friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
+void write_file(Tox *m, int friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length, void *userdata)
 {
     if (file_recv[filenumber].file != 0)
         if (fwrite(data, length, 1, file_recv[filenumber].file) != 1)
diff --git a/toxav/msi.c b/toxav/msi.c
index 9695029a..ee7a95f3 100644
--- a/toxav/msi.c
+++ b/toxav/msi.c
@@ -1002,18 +1002,18 @@ int send_error ( MSISession *session, MSICall *call, MSICallError errid, uint32_
  */
 void add_peer( MSICall *call, int peer_id )
 {
-    uint32_t* peers = !call->peers ? peers = calloc(sizeof(uint32_t), 1) :
-    realloc( call->peers, sizeof(uint32_t) * call->peer_count);
-        
+    uint32_t *peers = !call->peers ? peers = calloc(sizeof(uint32_t), 1) :
+                      realloc( call->peers, sizeof(uint32_t) * call->peer_count);
+
     if (!peers) {
         LOGGER_WARNING("Allocation failed! Program might misbehave!");
         return;
     }
-    
+
     call->peer_count ++;
     call->peers = peers;
     call->peers[call->peer_count - 1] = peer_id;
-    
+
     LOGGER_DEBUG("Added peer: %d", peer_id);
 }
 
@@ -1038,12 +1038,12 @@ MSICall *init_call ( MSISession *session, int peers, int ringing_timeout )
 
     for (; _call_idx < session->max_calls; _call_idx ++) {
         if ( !session->calls[_call_idx] ) {
-            
+
             if (!(session->calls[_call_idx] = calloc ( sizeof ( MSICall ), 1 ))) {
                 LOGGER_WARNING("Allocation failed! Program might misbehave!");
                 return NULL;
             }
-            
+
             break;
         }
     }
@@ -1455,7 +1455,7 @@ int handle_recv_error ( MSISession *session, MSICall *call, MSIMessage *msg )
  *
  *
  */
-void msi_handle_packet ( Messenger *messenger, int source, uint8_t *data, uint16_t length, void *object )
+void msi_handle_packet ( Messenger *messenger, int source, const uint8_t *data, uint16_t length, void *object )
 {
     LOGGER_DEBUG("Got msi message");
     /* Unused */
@@ -1610,7 +1610,7 @@ MSISession *msi_init_session ( Messenger *messenger, int32_t max_calls )
         free(_retu);
         return NULL;
     }
-    
+
     _retu->max_calls = max_calls;
 
     _retu->frequ = 10000; /* default value? */
@@ -1663,8 +1663,6 @@ int msi_terminate_session ( MSISession *session )
     timer_terminate_session(session->timer_handler);
     
     pthread_mutex_destroy(&session->mutex);
-
-//     timer_terminate_session();
     
     LOGGER_DEBUG("Terminated session: %p", session);
     free ( session );
diff --git a/toxav/rtp.c b/toxav/rtp.c
index ca37bf47..9ba3b6a3 100644
--- a/toxav/rtp.c
+++ b/toxav/rtp.c
@@ -105,16 +105,16 @@ RTPHeader *extract_header ( const uint8_t *payload, int length )
     }
 
     RTPHeader *_retu = calloc(1, sizeof (RTPHeader));
-    
+
     if ( !_retu ) {
         LOGGER_WARNING("Alloc failed! Program might misbehave!");
         return NULL;
     }
-    
+
     bytes_to_U16(&_retu->sequnum, payload);
 
     const uint8_t *_it = payload + 2;
-    
+
     _retu->flags = *_it;
     ++_it;
 
@@ -178,7 +178,7 @@ RTPExtHeader *extract_ext_header ( const uint8_t *payload, uint16_t length )
     const uint8_t *_it = payload;
 
     RTPExtHeader *_retu = calloc(1, sizeof (RTPExtHeader));
-    
+
     if ( !_retu ) {
         LOGGER_WARNING("Alloc failed! Program might misbehave!");
         return NULL;
@@ -290,7 +290,7 @@ uint8_t *add_ext_header ( RTPExtHeader *header, uint8_t *payload )
 RTPHeader *build_header ( RTPSession *session )
 {
     RTPHeader *_retu = calloc ( 1, sizeof (RTPHeader) );
-    
+
     if ( !_retu ) {
         LOGGER_WARNING("Alloc failed! Program might misbehave!");
         return NULL;
@@ -386,7 +386,7 @@ RTPMessage *msg_parse ( const uint8_t *data, int length )
  * @retval -1 Error occurred.
  * @retval 0 Success.
  */
-int rtp_handle_packet ( void *object, uint8_t *data, uint32_t length )
+int rtp_handle_packet ( void *object, const uint8_t *data, uint32_t length )
 {
     RTPSession *_session = object;
     RTPMessage *_msg;
@@ -451,7 +451,7 @@ RTPMessage *rtp_new_message ( RTPSession *session, const uint8_t *data, uint32_t
 
     uint8_t *_from_pos;
     RTPMessage *_retu = calloc(1, sizeof (RTPMessage));
-    
+
     if ( !_retu ) {
         LOGGER_WARNING("Alloc failed! Program might misbehave!");
         return NULL;
@@ -465,7 +465,7 @@ RTPMessage *rtp_new_message ( RTPSession *session, const uint8_t *data, uint32_t
     uint32_t _total_length = length + _retu->header->length + 1;
 
     _retu->data[0] = session->prefix;
-    
+
     if ( _retu->ext_header ) {
         _total_length += ( 4 /* Minimum ext header len */ + _retu->ext_header->length * size_32 );
 
@@ -617,10 +617,10 @@ int rtp_send_msg ( RTPSession *session, Messenger *messenger, const uint8_t *dat
     }
 
 
-    /* Set sequ number */    
+    /* Set sequ number */
     session->sequnum = session->sequnum >= MAX_SEQU_NUM ? 0 : session->sequnum + 1;
     rtp_free_msg ( session, msg );
-    
+
     return 0;
 }
 
@@ -665,7 +665,7 @@ void rtp_free_msg ( RTPSession *session, RTPMessage *msg )
 RTPSession *rtp_init_session ( int payload_type, Messenger *messenger, int friend_num )
 {
     RTPSession *_retu = calloc(1, sizeof(RTPSession));
-    
+
     if ( !_retu ) {
         LOGGER_WARNING("Alloc failed! Program might misbehave!");
         return NULL;
diff --git a/toxav/toxav.c b/toxav/toxav.c
index 02c5a970..743d7fcf 100644
--- a/toxav/toxav.c
+++ b/toxav/toxav.c
@@ -447,7 +447,7 @@ inline__ int toxav_send_rtp_payload ( ToxAv *av, int32_t call_index, ToxAvCallTy
             /* number of pieces - 1*/
             uint8_t numparts = (length - 1) / VIDEOFRAME_PIECE_SIZE;
 
-            uint8_t load[3 + VIDEOFRAME_PIECE_SIZE];
+            uint8_t load[2 + VIDEOFRAME_PIECE_SIZE];
             load[0] = av->calls[call_index].frame_outid++;
             load[1] = 0;
 
@@ -569,11 +569,11 @@ inline__ int toxav_recv_video ( ToxAv *av, int32_t call_index, vpx_image_t **out
             call->frame_limit = 0;
 
             if (rc != VPX_CODEC_OK) {
-                LOGGER_ERROR("Error decoding video: %s\n", vpx_codec_err_to_string(rc));
-                return ErrorInternal;
+                LOGGER_ERROR("Error decoding video: %u %s\n", i, vpx_codec_err_to_string(rc));
             }
         } else {
             /* old packet, dont read */
+            LOGGER_DEBUG("Old packet: %u\n", i);
             continue;
         }
 
@@ -583,12 +583,14 @@ inline__ int toxav_recv_video ( ToxAv *av, int32_t call_index, vpx_image_t **out
             continue;
         }
 
+        LOGGER_DEBUG("Video Packet: %u %u\n", packet[0], packet[1]);
         memcpy(call->frame_buf + packet[1] * VIDEOFRAME_PIECE_SIZE, packet + VIDEOFRAME_HEADER_SIZE,
                recved_size - VIDEOFRAME_HEADER_SIZE);
         uint32_t limit = packet[1] * VIDEOFRAME_PIECE_SIZE + recved_size - VIDEOFRAME_HEADER_SIZE;
 
         if (limit > call->frame_limit) {
             call->frame_limit = limit;
+            LOGGER_DEBUG("Limit: %u\n", call->frame_limit);
         }
     }
 
diff --git a/toxcore/DHT.c b/toxcore/DHT.c
index 133e9392..77d126c1 100644
--- a/toxcore/DHT.c
+++ b/toxcore/DHT.c
@@ -2212,7 +2212,7 @@ static int random_node_fromlist(Client_data *list, uint16_t list_size, Node_form
  *
  * TODO: remove the LAN stuff from this.
  */
-uint16_t random_nodes_path(DHT *dht, Node_format *nodes, uint16_t max_num)
+uint16_t random_nodes_path(const DHT *dht, Node_format *nodes, uint16_t max_num)
 {
     if (max_num == 0)
         return 0;
diff --git a/toxcore/DHT.h b/toxcore/DHT.h
index c7fddb4f..ea94e4ca 100644
--- a/toxcore/DHT.h
+++ b/toxcore/DHT.h
@@ -306,7 +306,7 @@ uint16_t closelist_nodes(DHT *dht, Node_format *nodes, uint16_t max_num);
  *
  * NOTE:this is used to pick nodes for paths.
  */
-uint16_t random_nodes_path(DHT *dht, Node_format *nodes, uint16_t max_num);
+uint16_t random_nodes_path(const DHT *dht, Node_format *nodes, uint16_t max_num);
 
 /* Run this function at least a couple times per second (It's the main loop). */
 void do_DHT(DHT *dht);
diff --git a/toxcore/Messenger.c b/toxcore/Messenger.c
index e9a66272..4344fdcb 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -40,10 +40,11 @@
 
 
 static void set_friend_status(Messenger *m, int32_t friendnumber, uint8_t status);
-static int write_cryptpacket_id(Messenger *m, int32_t friendnumber, uint8_t packet_id, uint8_t *data, uint32_t length);
+static int write_cryptpacket_id(const Messenger *m, int32_t friendnumber, uint8_t packet_id, const uint8_t *data,
+                                uint32_t length);
 
 // friend_not_valid determines if the friendnumber passed is valid in the Messenger object
-static uint8_t friend_not_valid(Messenger *m, int32_t friendnumber)
+static uint8_t friend_not_valid(const Messenger *m, int32_t friendnumber)
 {
     return (unsigned int)friendnumber >= m->numfriends;
 }
@@ -109,7 +110,7 @@ int32_t getfriend_id(const Messenger *m, const uint8_t *client_id)
  *  return 0 if success.
  *  return -1 if failure.
  */
-int getclient_id(Messenger *m, int32_t friendnumber, uint8_t *client_id)
+int getclient_id(const Messenger *m, int32_t friendnumber, uint8_t *client_id)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -125,7 +126,7 @@ int getclient_id(Messenger *m, int32_t friendnumber, uint8_t *client_id)
  *
  *  return a uint16_t that represents the checksum of address of length len.
  */
-static uint16_t address_checksum(uint8_t *address, uint32_t len)
+static uint16_t address_checksum(const uint8_t *address, uint32_t len)
 {
     uint8_t checksum[2] = {0};
     uint16_t check;
@@ -142,7 +143,7 @@ static uint16_t address_checksum(uint8_t *address, uint32_t len)
  *
  *  return FRIEND_ADDRESS_SIZE byte address to give to others.
  */
-void getaddress(Messenger *m, uint8_t *address)
+void getaddress(const Messenger *m, uint8_t *address)
 {
     id_copy(address, m->net_crypto->self_public_key);
     uint32_t nospam = get_nospam(&(m->fr));
@@ -152,7 +153,7 @@ void getaddress(Messenger *m, uint8_t *address)
 }
 
 /* callback for recv TCP relay nodes. */
-static int tcp_relay_node_callback(void *object, uint32_t number, IP_Port ip_port, uint8_t *public_key)
+static int tcp_relay_node_callback(void *object, uint32_t number, IP_Port ip_port, const uint8_t *public_key)
 {
     Messenger *m = object;
 
@@ -183,7 +184,7 @@ static int tcp_relay_node_callback(void *object, uint32_t number, IP_Port ip_por
  *  (the nospam for that friend was set to the new one).
  *  return FAERR_NOMEM if increasing the friend list size fails.
  */
-int32_t m_addfriend(Messenger *m, uint8_t *address, uint8_t *data, uint16_t length)
+int32_t m_addfriend(Messenger *m, const uint8_t *address, const uint8_t *data, uint16_t length)
 {
     if (length > MAX_FRIEND_REQUEST_DATA_SIZE)
         return FAERR_TOOLONG;
@@ -346,7 +347,7 @@ int m_delfriend(Messenger *m, int32_t friendnumber)
     return 0;
 }
 
-int m_get_friend_connectionstatus(Messenger *m, int32_t friendnumber)
+int m_get_friend_connectionstatus(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -354,7 +355,7 @@ int m_get_friend_connectionstatus(Messenger *m, int32_t friendnumber)
     return m->friendlist[friendnumber].status == FRIEND_ONLINE;
 }
 
-int m_friend_exists(Messenger *m, int32_t friendnumber)
+int m_friend_exists(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return 0;
@@ -402,7 +403,7 @@ uint32_t m_sendmessage_withid(Messenger *m, int32_t friendnumber, uint32_t theid
  *  return the message id if packet was successfully put into the send queue.
  *  return 0 if it was not.
  */
-uint32_t m_sendaction(Messenger *m, int32_t friendnumber, uint8_t *action, uint32_t length)
+uint32_t m_sendaction(Messenger *m, int32_t friendnumber, const uint8_t *action, uint32_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return 0;
@@ -419,7 +420,8 @@ uint32_t m_sendaction(Messenger *m, int32_t friendnumber, uint8_t *action, uint3
     return 0;
 }
 
-uint32_t m_sendaction_withid(Messenger *m, int32_t friendnumber, uint32_t theid, uint8_t *action, uint32_t length)
+uint32_t m_sendaction_withid(const Messenger *m, int32_t friendnumber, uint32_t theid, const uint8_t *action,
+                             uint32_t length)
 {
     if (length >= (MAX_CRYPTO_DATA_SIZE - sizeof(theid)))
         return 0;
@@ -434,7 +436,7 @@ uint32_t m_sendaction_withid(Messenger *m, int32_t friendnumber, uint32_t theid,
 /* Send a name packet to friendnumber.
  * length is the length with the NULL terminator.
  */
-static int m_sendname(Messenger *m, int32_t friendnumber, uint8_t *name, uint16_t length)
+static int m_sendname(const Messenger *m, int32_t friendnumber, const uint8_t *name, uint16_t length)
 {
     if (length > MAX_NAME_LENGTH || length == 0)
         return 0;
@@ -447,7 +449,7 @@ static int m_sendname(Messenger *m, int32_t friendnumber, uint8_t *name, uint16_
  *  return 0 if success.
  *  return -1 if failure.
  */
-int setfriendname(Messenger *m, int32_t friendnumber, uint8_t *name, uint16_t length)
+int setfriendname(Messenger *m, int32_t friendnumber, const uint8_t *name, uint16_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -492,7 +494,7 @@ int setname(Messenger *m, const uint8_t *name, uint16_t length)
  *
  *  return the length of the name.
  */
-uint16_t getself_name(Messenger *m, uint8_t *name)
+uint16_t getself_name(const Messenger *m, uint8_t *name)
 {
     if (name == NULL) {
         return 0;
@@ -509,7 +511,7 @@ uint16_t getself_name(Messenger *m, uint8_t *name)
  *  return length of name if success.
  *  return -1 if failure.
  */
-int getname(Messenger *m, int32_t friendnumber, uint8_t *name)
+int getname(const Messenger *m, int32_t friendnumber, uint8_t *name)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -518,7 +520,7 @@ int getname(Messenger *m, int32_t friendnumber, uint8_t *name)
     return m->friendlist[friendnumber].name_length;
 }
 
-int m_get_name_size(Messenger *m, int32_t friendnumber)
+int m_get_name_size(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -526,7 +528,7 @@ int m_get_name_size(Messenger *m, int32_t friendnumber)
     return m->friendlist[friendnumber].name_length;
 }
 
-int m_get_self_name_size(Messenger *m)
+int m_get_self_name_size(const Messenger *m)
 {
     return m->name_length;
 }
@@ -565,7 +567,7 @@ int m_set_userstatus(Messenger *m, uint8_t status)
 /* return the size of friendnumber's user status.
  * Guaranteed to be at most MAX_STATUSMESSAGE_LENGTH.
  */
-int m_get_statusmessage_size(Messenger *m, int32_t friendnumber)
+int m_get_statusmessage_size(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -576,7 +578,7 @@ int m_get_statusmessage_size(Messenger *m, int32_t friendnumber)
 /*  Copy the user status of friendnumber into buf, truncating if needed to maxlen
  *  bytes, use m_get_statusmessage_size to find out how much you need to allocate.
  */
-int m_copy_statusmessage(Messenger *m, int32_t friendnumber, uint8_t *buf, uint32_t maxlen)
+int m_copy_statusmessage(const Messenger *m, int32_t friendnumber, uint8_t *buf, uint32_t maxlen)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -591,12 +593,12 @@ int m_copy_statusmessage(Messenger *m, int32_t friendnumber, uint8_t *buf, uint3
 /* return the size of friendnumber's user status.
  * Guaranteed to be at most MAX_STATUSMESSAGE_LENGTH.
  */
-int m_get_self_statusmessage_size(Messenger *m)
+int m_get_self_statusmessage_size(const Messenger *m)
 {
     return m->statusmessage_length;
 }
 
-int m_copy_self_statusmessage(Messenger *m, uint8_t *buf, uint32_t maxlen)
+int m_copy_self_statusmessage(const Messenger *m, uint8_t *buf, uint32_t maxlen)
 {
     int msglen = MIN(maxlen, m->statusmessage_length);
     memcpy(buf, m->statusmessage, msglen);
@@ -604,7 +606,7 @@ int m_copy_self_statusmessage(Messenger *m, uint8_t *buf, uint32_t maxlen)
     return msglen;
 }
 
-uint8_t m_get_userstatus(Messenger *m, int32_t friendnumber)
+uint8_t m_get_userstatus(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return USERSTATUS_INVALID;
@@ -618,12 +620,12 @@ uint8_t m_get_userstatus(Messenger *m, int32_t friendnumber)
     return status;
 }
 
-uint8_t m_get_self_userstatus(Messenger *m)
+uint8_t m_get_self_userstatus(const Messenger *m)
 {
     return m->userstatus;
 }
 
-uint64_t m_get_last_online(Messenger *m, int32_t friendnumber)
+uint64_t m_get_last_online(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -647,7 +649,7 @@ int m_set_usertyping(Messenger *m, int32_t friendnumber, uint8_t is_typing)
     return 0;
 }
 
-uint8_t m_get_istyping(Messenger *m, int32_t friendnumber)
+uint8_t m_get_istyping(const Messenger *m, int32_t friendnumber)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -655,23 +657,23 @@ uint8_t m_get_istyping(Messenger *m, int32_t friendnumber)
     return m->friendlist[friendnumber].is_typing;
 }
 
-static int send_statusmessage(Messenger *m, int32_t friendnumber, uint8_t *status, uint16_t length)
+static int send_statusmessage(const Messenger *m, int32_t friendnumber, const uint8_t *status, uint16_t length)
 {
     return write_cryptpacket_id(m, friendnumber, PACKET_ID_STATUSMESSAGE, status, length);
 }
 
-static int send_userstatus(Messenger *m, int32_t friendnumber, uint8_t status)
+static int send_userstatus(const Messenger *m, int32_t friendnumber, uint8_t status)
 {
     return write_cryptpacket_id(m, friendnumber, PACKET_ID_USERSTATUS, &status, sizeof(status));
 }
 
-static int send_user_istyping(Messenger *m, int32_t friendnumber, uint8_t is_typing)
+static int send_user_istyping(const Messenger *m, int32_t friendnumber, uint8_t is_typing)
 {
     uint8_t typing = is_typing;
     return write_cryptpacket_id(m, friendnumber, PACKET_ID_TYPING, &typing, sizeof(typing));
 }
 
-static int send_ping(Messenger *m, int32_t friendnumber)
+static int send_ping(const Messenger *m, int32_t friendnumber)
 {
     int ret = write_cryptpacket_id(m, friendnumber, PACKET_ID_ALIVE, 0, 0);
 
@@ -681,7 +683,7 @@ static int send_ping(Messenger *m, int32_t friendnumber)
     return ret;
 }
 
-static int send_relays(Messenger *m, int32_t friendnumber)
+static int send_relays(const Messenger *m, int32_t friendnumber)
 {
     Node_format nodes[MAX_SHARED_RELAYS];
     uint8_t data[1024];
@@ -700,7 +702,7 @@ static int send_relays(Messenger *m, int32_t friendnumber)
 
 
 
-static int set_friend_statusmessage(Messenger *m, int32_t friendnumber, uint8_t *status, uint16_t length)
+static int set_friend_statusmessage(const Messenger *m, int32_t friendnumber, const uint8_t *status, uint16_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -713,12 +715,12 @@ static int set_friend_statusmessage(Messenger *m, int32_t friendnumber, uint8_t
     return 0;
 }
 
-static void set_friend_userstatus(Messenger *m, int32_t friendnumber, uint8_t status)
+static void set_friend_userstatus(const Messenger *m, int32_t friendnumber, uint8_t status)
 {
     m->friendlist[friendnumber].userstatus = status;
 }
 
-static void set_friend_typing(Messenger *m, int32_t friendnumber, uint8_t is_typing)
+static void set_friend_typing(const Messenger *m, int32_t friendnumber, uint8_t is_typing)
 {
     m->friendlist[friendnumber].is_typing = is_typing;
 }
@@ -745,28 +747,28 @@ void m_callback_friendrequest(Messenger *m, void (*function)(Messenger *m, const
 }
 
 /* Set the function that will be executed when a message from a friend is received. */
-void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata)
 {
     m->friend_message = function;
     m->friend_message_userdata = userdata;
 }
 
-void m_callback_action(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_action(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                        void *userdata)
 {
     m->friend_action = function;
     m->friend_action_userdata = userdata;
 }
 
-void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                            void *userdata)
 {
     m->friend_namechange = function;
     m->friend_namechange_userdata = userdata;
 }
 
-void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata)
 {
     m->friend_statusmessagechange = function;
@@ -804,7 +806,7 @@ void m_callback_connectionstatus_internal_av(Messenger *m, void (*function)(Mess
     m->friend_connectionstatuschange_internal_userdata = userdata;
 }
 
-static void break_files(Messenger *m, int32_t friendnumber);
+static void break_files(const Messenger *m, int32_t friendnumber);
 static void check_friend_connectionstatus(Messenger *m, int32_t friendnumber, uint8_t status)
 {
     if (status == NOFRIEND)
@@ -840,7 +842,8 @@ void set_friend_status(Messenger *m, int32_t friendnumber, uint8_t status)
     m->friendlist[friendnumber].status = status;
 }
 
-int write_cryptpacket_id(Messenger *m, int32_t friendnumber, uint8_t packet_id, uint8_t *data, uint32_t length)
+int write_cryptpacket_id(const Messenger *m, int32_t friendnumber, uint8_t packet_id, const uint8_t *data,
+                         uint32_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return 0;
@@ -862,7 +865,7 @@ int write_cryptpacket_id(Messenger *m, int32_t friendnumber, uint8_t packet_id,
 /* return 1 if the groupnumber is not valid.
  * return 0 if the groupnumber is valid.
  */
-static uint8_t groupnumber_not_valid(Messenger *m, int groupnumber)
+static uint8_t groupnumber_not_valid(const Messenger *m, int groupnumber)
 {
     if ((unsigned int)groupnumber >= m->numchats)
         return 1;
@@ -880,7 +883,7 @@ static uint8_t groupnumber_not_valid(Messenger *m, int groupnumber)
 /* returns valid ip port of connected friend on success
  * returns zeroed out IP_Port on failure
  */
-static IP_Port get_friend_ipport(Messenger *m, int32_t friendnumber)
+static IP_Port get_friend_ipport(const Messenger *m, int32_t friendnumber)
 {
     IP_Port zero;
     memset(&zero, 0, sizeof(zero));
@@ -904,7 +907,7 @@ static IP_Port get_friend_ipport(Messenger *m, int32_t friendnumber)
 /* returns the group number of the chat with public key group_public_key.
  * returns -1 on failure.
  */
-static int group_num(Messenger *m, uint8_t *group_public_key)
+static int group_num(const Messenger *m, const uint8_t *group_public_key)
 {
     uint32_t i;
 
@@ -921,7 +924,8 @@ static int group_num(Messenger *m, uint8_t *group_public_key)
  *
  *  Function(Messenger *m, int32_t friendnumber, uint8_t *group_public_key, void *userdata)
  */
-void m_callback_group_invite(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, void *), void *userdata)
+void m_callback_group_invite(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, void *),
+                             void *userdata)
 {
     m->group_invite = function;
     m->group_invite_userdata = userdata;
@@ -931,7 +935,7 @@ void m_callback_group_invite(Messenger *m, void (*function)(Messenger *m, int32_
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void m_callback_group_message(Messenger *m, void (*function)(Messenger *m, int, int, uint8_t *, uint16_t, void *),
+void m_callback_group_message(Messenger *m, void (*function)(Messenger *m, int, int, const uint8_t *, uint16_t, void *),
                               void *userdata)
 {
     m->group_message = function;
@@ -942,7 +946,7 @@ void m_callback_group_message(Messenger *m, void (*function)(Messenger *m, int,
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void m_callback_group_action(Messenger *m, void (*function)(Messenger *m, int, int, uint8_t *, uint16_t, void *),
+void m_callback_group_action(Messenger *m, void (*function)(Messenger *m, int, int, const uint8_t *, uint16_t, void *),
                              void *userdata)
 {
     m->group_action = function;
@@ -961,7 +965,7 @@ void m_callback_group_namelistchange(Messenger *m, void (*function)(Messenger *m
     m->group_namelistchange_userdata = userdata;
 }
 
-static int get_chat_num(Messenger *m, Group_Chat *chat)
+static int get_chat_num(const Messenger *m, const Group_Chat *chat)
 {
     uint32_t i;
 
@@ -1114,7 +1118,7 @@ int del_groupchat(Messenger *m, int groupnumber)
  * return length of name if success
  * return -1 if failure
  */
-int m_group_peername(Messenger *m, int groupnumber, int peernumber, uint8_t *name)
+int m_group_peername(const Messenger *m, int groupnumber, int peernumber, uint8_t *name)
 {
     if ((unsigned int)groupnumber >= m->numchats)
         return -1;
@@ -1141,7 +1145,7 @@ static void group_store_friendinvite(Messenger *m, int32_t friendnumber, int gro
 /* return 1 if that friend was invited to the group
  * return 0 if the friend was not or error.
  */
-static uint8_t group_invited(Messenger *m, int32_t friendnumber, int groupnumber)
+static uint8_t group_invited(const Messenger *m, int32_t friendnumber, int groupnumber)
 {
 
     uint32_t i;
@@ -1189,7 +1193,7 @@ int invite_friend(Messenger *m, int32_t friendnumber, int groupnumber)
  * returns group number on success
  * returns -1 on failure.
  */
-int join_groupchat(Messenger *m, int32_t friendnumber, uint8_t *friend_group_public_key)
+int join_groupchat(Messenger *m, int32_t friendnumber, const uint8_t *friend_group_public_key)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1222,7 +1226,7 @@ int join_groupchat(Messenger *m, int32_t friendnumber, uint8_t *friend_group_pub
  * return 0 on success
  * return -1 on failure
  */
-int group_message_send(Messenger *m, int groupnumber, uint8_t *message, uint32_t length)
+int group_message_send(const Messenger *m, int groupnumber, const uint8_t *message, uint32_t length)
 {
     if (groupnumber_not_valid(m, groupnumber))
         return -1;
@@ -1237,7 +1241,7 @@ int group_message_send(Messenger *m, int groupnumber, uint8_t *message, uint32_t
  * return 0 on success
  * return -1 on failure
  */
-int group_action_send(Messenger *m, int groupnumber, uint8_t *action, uint32_t length)
+int group_action_send(const Messenger *m, int groupnumber, const uint8_t *action, uint32_t length)
 {
     if (groupnumber_not_valid(m, groupnumber))
         return -1;
@@ -1251,7 +1255,7 @@ int group_action_send(Messenger *m, int groupnumber, uint8_t *action, uint32_t l
 /* Return the number of peers in the group chat on success.
  * return -1 on failure
  */
-int group_number_peers(Messenger *m, int groupnumber)
+int group_number_peers(const Messenger *m, int groupnumber)
 {
     if (groupnumber_not_valid(m, groupnumber))
         return -1;
@@ -1269,7 +1273,8 @@ int group_number_peers(Messenger *m, int groupnumber)
  *
  * return -1 on failure.
  */
-int group_names(Messenger *m, int groupnumber, uint8_t names[][MAX_NICK_BYTES], uint16_t lengths[], uint16_t length)
+int group_names(const Messenger *m, int groupnumber, uint8_t names[][MAX_NICK_BYTES], uint16_t lengths[],
+                uint16_t length)
 {
     if (groupnumber_not_valid(m, groupnumber))
         return -1;
@@ -1315,7 +1320,7 @@ static void do_allgroupchats(Messenger *m)
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length, void *userdata)
  */
-void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint64_t, uint8_t *,
+void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint64_t, const uint8_t *,
                                uint16_t, void *), void *userdata)
 {
     m->file_sendrequest = function;
@@ -1327,8 +1332,8 @@ void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int3
  *  Function(Tox *tox, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t control_type, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void callback_file_control(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t, uint8_t, uint8_t *,
-                           uint16_t, void *), void *userdata)
+void callback_file_control(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t, uint8_t,
+                           const uint8_t *, uint16_t, void *), void *userdata)
 {
     m->file_filecontrol = function;
     m->file_filecontrol_userdata = userdata;
@@ -1339,7 +1344,7 @@ void callback_file_control(Messenger *m, void (*function)(Messenger *m, int32_t,
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, uint16_t length,
+void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, const uint8_t *, uint16_t length,
                         void *), void *userdata)
 {
     m->file_filedata = function;
@@ -1353,8 +1358,8 @@ void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, ui
  *  return 1 on success
  *  return 0 on failure
  */
-int file_sendrequest(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename,
-                     uint16_t filename_length)
+int file_sendrequest(const Messenger *m, int32_t friendnumber, uint8_t filenumber, uint64_t filesize,
+                     const uint8_t *filename, uint16_t filename_length)
 {
     if (friend_not_valid(m, friendnumber))
         return 0;
@@ -1376,7 +1381,8 @@ int file_sendrequest(Messenger *m, int32_t friendnumber, uint8_t filenumber, uin
  *  return file number on success
  *  return -1 on failure
  */
-int new_filesender(Messenger *m, int32_t friendnumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length)
+int new_filesender(const Messenger *m, int32_t friendnumber, uint64_t filesize, const uint8_t *filename,
+                   uint16_t filename_length)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1406,8 +1412,8 @@ int new_filesender(Messenger *m, int32_t friendnumber, uint64_t filesize, uint8_
  *  return 0 on success
  *  return -1 on failure
  */
-int file_control(Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
-                 uint8_t *data, uint16_t length)
+int file_control(const Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
+                 const uint8_t *data, uint16_t length)
 {
     if (length > MAX_CRYPTO_DATA_SIZE - 3)
         return -1;
@@ -1494,7 +1500,7 @@ int file_control(Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8
  *  return 0 on success
  *  return -1 on failure
  */
-int file_data(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length)
+int file_data(const Messenger *m, int32_t friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length)
 {
     if (length > MAX_CRYPTO_DATA_SIZE - 1)
         return -1;
@@ -1529,7 +1535,7 @@ int file_data(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t *d
  *  return number of bytes remaining to be sent/received on success
  *  return 0 on failure
  */
-uint64_t file_dataremaining(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive)
+uint64_t file_dataremaining(const Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive)
 {
     if (friend_not_valid(m, friendnumber))
         return 0;
@@ -1552,7 +1558,7 @@ uint64_t file_dataremaining(Messenger *m, int32_t friendnumber, uint8_t filenumb
 /* Run this when the friend disconnects.
  *  Sets all current file transfers to broken.
  */
-static void break_files(Messenger *m, int32_t friendnumber)
+static void break_files(const Messenger *m, int32_t friendnumber)
 {
     uint32_t i;
 
@@ -1565,7 +1571,7 @@ static void break_files(Messenger *m, int32_t friendnumber)
     }
 }
 
-static int handle_filecontrol(Messenger *m, int32_t friendnumber, uint8_t receive_send, uint8_t filenumber,
+static int handle_filecontrol(const Messenger *m, int32_t friendnumber, uint8_t receive_send, uint8_t filenumber,
                               uint8_t message_id, uint8_t *data,
                               uint16_t length)
 {
@@ -1655,7 +1661,7 @@ static int handle_filecontrol(Messenger *m, int32_t friendnumber, uint8_t receiv
  *
  *  Function(Messenger *m, int friendnumber, uint8_t *data, uint16_t length, void *userdata)
  */
-void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                            void *userdata)
 {
     m->msi_packet = function;
@@ -1667,12 +1673,12 @@ void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t,
  *  return 1 on success
  *  return 0 on failure
  */
-int m_msi_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint16_t length)
+int m_msi_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint16_t length)
 {
     return write_cryptpacket_id(m, friendnumber, PACKET_ID_MSI, data, length);
 }
 
-static int handle_custom_lossy_packet(void *object, int friend_num, uint8_t *packet, uint16_t length)
+static int handle_custom_lossy_packet(void *object, int friend_num, const uint8_t *packet, uint16_t length)
 {
     Messenger *m = object;
 
@@ -1687,7 +1693,7 @@ static int handle_custom_lossy_packet(void *object, int friend_num, uint8_t *pac
 }
 
 int custom_lossy_packet_registerhandler(Messenger *m, int32_t friendnumber, uint8_t byte,
-                                        int (*packet_handler_callback)(void *object, uint8_t *data, uint32_t len), void *object)
+                                        int (*packet_handler_callback)(void *object, const uint8_t *data, uint32_t len), void *object)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1703,7 +1709,7 @@ int custom_lossy_packet_registerhandler(Messenger *m, int32_t friendnumber, uint
     return 0;
 }
 
-int send_custom_lossy_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint32_t length)
+int send_custom_lossy_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint32_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1717,7 +1723,7 @@ int send_custom_lossy_packet(Messenger *m, int32_t friendnumber, uint8_t *data,
     return send_lossy_cryptpacket(m->net_crypto, m->friendlist[friendnumber].crypt_connection_id, data, length);
 }
 
-static int handle_custom_lossless_packet(void *object, int friend_num, uint8_t *packet, uint16_t length)
+static int handle_custom_lossless_packet(void *object, int friend_num, const uint8_t *packet, uint16_t length)
 {
     Messenger *m = object;
 
@@ -1738,7 +1744,7 @@ static int handle_custom_lossless_packet(void *object, int friend_num, uint8_t *
 }
 
 int custom_lossless_packet_registerhandler(Messenger *m, int32_t friendnumber, uint8_t byte,
-        int (*packet_handler_callback)(void *object, uint8_t *data, uint32_t len), void *object)
+        int (*packet_handler_callback)(void *object, const uint8_t *data, uint32_t len), void *object)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1755,7 +1761,7 @@ int custom_lossless_packet_registerhandler(Messenger *m, int32_t friendnumber, u
     return 0;
 }
 
-int send_custom_lossless_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint32_t length)
+int send_custom_lossless_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint32_t length)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -1772,7 +1778,7 @@ int send_custom_lossless_packet(Messenger *m, int32_t friendnumber, uint8_t *dat
 /* Function to filter out some friend requests*/
 static int friend_already_added(const uint8_t *client_id, void *data)
 {
-    Messenger *m = data;
+    const Messenger *m = data;
 
     if (getfriend_id(m, client_id) == -1)
         return 0;
@@ -2029,13 +2035,13 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
         }
 
         case PACKET_ID_MESSAGE: {
-            uint8_t *message_id = data;
+            const uint8_t *message_id = data;
             uint8_t message_id_length = 4;
 
             if (data_length <= message_id_length)
                 break;
 
-            uint8_t *message = data + message_id_length;
+            const uint8_t *message = data + message_id_length;
             uint16_t message_length = data_length - message_id_length;
 
             /* Make sure the NULL terminator is present. */
@@ -2054,13 +2060,13 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
         }
 
         case PACKET_ID_ACTION: {
-            uint8_t *message_id = data;
+            const uint8_t *message_id = data;
             uint8_t message_id_length = 4;
 
             if (data_length <= message_id_length)
                 break;
 
-            uint8_t *action = data + message_id_length;
+            const uint8_t *action = data + message_id_length;
             uint16_t action_length = data_length - message_id_length;
 
             /* Make sure the NULL terminator is present. */
@@ -2128,8 +2134,8 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
 
             uint8_t filenumber = data[0];
             uint64_t filesize;
-            net_to_host(data + 1, sizeof(filesize));
             memcpy(&filesize, data + 1, sizeof(filesize));
+            net_to_host((uint8_t *) &filesize, sizeof(filesize));
             m->friendlist[i].file_receiving[filenumber].status = FILESTATUS_NOT_ACCEPTED;
             m->friendlist[i].file_receiving[filenumber].size = filesize;
             m->friendlist[i].file_receiving[filenumber].transferred = 0;
@@ -2216,7 +2222,7 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
     return 0;
 }
 
-static int friend_new_connection(Messenger *m, int32_t friendnumber, uint8_t *real_public_key)
+static int friend_new_connection(Messenger *m, int32_t friendnumber, const uint8_t *real_public_key)
 {
     if (friend_not_valid(m, friendnumber))
         return -1;
@@ -2337,7 +2343,7 @@ void do_friends(Messenger *m)
 #define DUMPING_CLIENTS_FRIENDS_EVERY_N_SECONDS 60UL
 static time_t lastdump = 0;
 static char IDString[CLIENT_ID_SIZE * 2 + 1];
-static char *ID2String(uint8_t *client_id)
+static char *ID2String(const uint8_t *client_id)
 {
     uint32_t i;
 
@@ -2349,7 +2355,7 @@ static char *ID2String(uint8_t *client_id)
 }
 #endif
 
-/* Minimum messenger run interval in ms 
+/* Minimum messenger run interval in ms
    TODO: A/V */
 #define MIN_RUN_INTERVAL 50
 
@@ -2530,12 +2536,12 @@ struct SAVED_FRIEND {
     uint64_t ping_lastrecv;
 };
 
-static uint32_t saved_friendslist_size(Messenger *m)
+static uint32_t saved_friendslist_size(const Messenger *m)
 {
     return count_friendlist(m) * sizeof(struct SAVED_FRIEND);
 }
 
-static uint32_t friends_list_save(Messenger *m, uint8_t *data)
+static uint32_t friends_list_save(const Messenger *m, uint8_t *data)
 {
     uint32_t i;
     uint32_t num = 0;
@@ -2614,7 +2620,7 @@ static int friends_list_load(Messenger *m, const uint8_t *data, uint32_t length)
 }
 
 /*  return size of the messenger data (for saving) */
-uint32_t messenger_size(Messenger *m)
+uint32_t messenger_size(const Messenger *m)
 {
     uint32_t size32 = sizeof(uint32_t), sizesubhead = size32 * 2;
     return   size32 * 2                                      // global cookie
@@ -2639,7 +2645,7 @@ static uint8_t *z_state_save_subheader(uint8_t *data, uint32_t len, uint16_t typ
 
 
 /* Save the messenger in data of size Messenger_size(). */
-void messenger_save(Messenger *m, uint8_t *data)
+void messenger_save(const Messenger *m, uint8_t *data)
 {
     uint32_t len;
     uint16_t type;
@@ -2776,7 +2782,7 @@ static int messenger_load_state_callback(void *outer, const uint8_t *data, uint3
 }
 
 /* Load the messenger from data of size length. */
-int messenger_load(Messenger *m, uint8_t *data, uint32_t length)
+int messenger_load(Messenger *m, const uint8_t *data, uint32_t length)
 {
     uint32_t data32[2];
     uint32_t cookie_len = sizeof(data32);
@@ -2796,7 +2802,7 @@ int messenger_load(Messenger *m, uint8_t *data, uint32_t length)
 /* Return the number of friends in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_friendlist. */
-uint32_t count_friendlist(Messenger *m)
+uint32_t count_friendlist(const Messenger *m)
 {
     uint32_t ret = 0;
     uint32_t i;
@@ -2811,7 +2817,7 @@ uint32_t count_friendlist(Messenger *m)
 }
 
 /* Return the number of online friends in the instance m. */
-uint32_t get_num_online_friends(Messenger *m)
+uint32_t get_num_online_friends(const Messenger *m)
 {
     return m->numonline_friends;
 }
@@ -2821,7 +2827,7 @@ uint32_t get_num_online_friends(Messenger *m)
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t copy_friendlist(Messenger *m, int32_t *out_list, uint32_t list_size)
+uint32_t copy_friendlist(Messenger const *m, int32_t *out_list, uint32_t list_size)
 {
     if (!out_list)
         return 0;
@@ -2853,7 +2859,7 @@ uint32_t copy_friendlist(Messenger *m, int32_t *out_list, uint32_t list_size)
  * retun 0 if success.
  * return -1 if failure.
  */
-int get_friendlist(Messenger *m, int32_t **out_list, uint32_t *out_list_length)
+int get_friendlist(const Messenger *m, int32_t **out_list, uint32_t *out_list_length)
 {
     uint32_t i;
 
@@ -2883,7 +2889,7 @@ int get_friendlist(Messenger *m, int32_t **out_list, uint32_t *out_list_length)
 /* Return the number of chats in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_chatlist. */
-uint32_t count_chatlist(Messenger *m)
+uint32_t count_chatlist(const Messenger *m)
 {
     uint32_t ret = 0;
     uint32_t i;
@@ -2902,7 +2908,7 @@ uint32_t count_chatlist(Messenger *m)
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t copy_chatlist(Messenger *m, int *out_list, uint32_t list_size)
+uint32_t copy_chatlist(const Messenger *m, int *out_list, uint32_t list_size)
 {
     if (!out_list)
         return 0;
diff --git a/toxcore/Messenger.h b/toxcore/Messenger.h
index e6ea59c1..ce0e5825 100644
--- a/toxcore/Messenger.h
+++ b/toxcore/Messenger.h
@@ -172,12 +172,12 @@ typedef struct {
     uint16_t invited_groups_num;
 
     struct {
-        int (*function)(void *object, uint8_t *data, uint32_t len);
+        int (*function)(void *object, const uint8_t *data, uint32_t len);
         void *object;
     } lossy_packethandlers[PACKET_ID_LOSSY_RANGE_SIZE];
 
     struct {
-        int (*function)(void *object, uint8_t *data, uint32_t len);
+        int (*function)(void *object, const uint8_t *data, uint32_t len);
         void *object;
     } lossless_packethandlers[PACKET_ID_LOSSLESS_RANGE_SIZE];
 } Friend;
@@ -212,13 +212,13 @@ typedef struct Messenger {
 
     uint64_t last_LANdiscovery;
 
-    void (*friend_message)(struct Messenger *m, int32_t, uint8_t *, uint16_t, void *);
+    void (*friend_message)(struct Messenger *m, int32_t, const uint8_t *, uint16_t, void *);
     void *friend_message_userdata;
-    void (*friend_action)(struct Messenger *m, int32_t, uint8_t *, uint16_t, void *);
+    void (*friend_action)(struct Messenger *m, int32_t, const uint8_t *, uint16_t, void *);
     void *friend_action_userdata;
-    void (*friend_namechange)(struct Messenger *m, int32_t, uint8_t *, uint16_t, void *);
+    void (*friend_namechange)(struct Messenger *m, int32_t, const uint8_t *, uint16_t, void *);
     void *friend_namechange_userdata;
-    void (*friend_statusmessagechange)(struct Messenger *m, int32_t, uint8_t *, uint16_t, void *);
+    void (*friend_statusmessagechange)(struct Messenger *m, int32_t, const uint8_t *, uint16_t, void *);
     void *friend_statusmessagechange_userdata;
     void (*friend_userstatuschange)(struct Messenger *m, int32_t, uint8_t, void *);
     void *friend_userstatuschange_userdata;
@@ -233,23 +233,23 @@ typedef struct Messenger {
     void (*friend_connectionstatuschange_internal)(struct Messenger *m, int32_t, uint8_t, void *);
     void *friend_connectionstatuschange_internal_userdata;
 
-    void (*group_invite)(struct Messenger *m, int32_t, uint8_t *, void *);
+    void (*group_invite)(struct Messenger *m, int32_t, const uint8_t *, void *);
     void *group_invite_userdata;
-    void (*group_message)(struct Messenger *m, int, int, uint8_t *, uint16_t, void *);
+    void (*group_message)(struct Messenger *m, int, int, const uint8_t *, uint16_t, void *);
     void *group_message_userdata;
-    void (*group_action)(struct Messenger *m, int, int, uint8_t *, uint16_t, void *);
+    void (*group_action)(struct Messenger *m, int, int, const uint8_t *, uint16_t, void *);
     void *group_action_userdata;
     void (*group_namelistchange)(struct Messenger *m, int, int, uint8_t, void *);
     void *group_namelistchange_userdata;
 
-    void (*file_sendrequest)(struct Messenger *m, int32_t, uint8_t, uint64_t, uint8_t *, uint16_t, void *);
+    void (*file_sendrequest)(struct Messenger *m, int32_t, uint8_t, uint64_t, const uint8_t *, uint16_t, void *);
     void *file_sendrequest_userdata;
-    void (*file_filecontrol)(struct Messenger *m, int32_t, uint8_t, uint8_t, uint8_t, uint8_t *, uint16_t, void *);
+    void (*file_filecontrol)(struct Messenger *m, int32_t, uint8_t, uint8_t, uint8_t, const uint8_t *, uint16_t, void *);
     void *file_filecontrol_userdata;
-    void (*file_filedata)(struct Messenger *m, int32_t, uint8_t, uint8_t *, uint16_t length, void *);
+    void (*file_filedata)(struct Messenger *m, int32_t, uint8_t, const uint8_t *, uint16_t length, void *);
     void *file_filedata_userdata;
 
-    void (*msi_packet)(struct Messenger *m, int32_t, uint8_t *, uint16_t, void *);
+    void (*msi_packet)(struct Messenger *m, int32_t, const uint8_t *, uint16_t, void *);
     void *msi_packet_userdata;
 
 } Messenger;
@@ -258,7 +258,7 @@ typedef struct Messenger {
  *
  *  return FRIEND_ADDRESS_SIZE byte address to give to others.
  */
-void getaddress(Messenger *m, uint8_t *address);
+void getaddress(const Messenger *m, uint8_t *address);
 
 /* Add a friend.
  * Set the data that will be sent along with friend request.
@@ -276,7 +276,7 @@ void getaddress(Messenger *m, uint8_t *address);
  *  (the nospam for that friend was set to the new one).
  *  return -8 if increasing the friend list size fails.
  */
-int32_t m_addfriend(Messenger *m, uint8_t *address, uint8_t *data, uint16_t length);
+int32_t m_addfriend(Messenger *m, const uint8_t *address, const uint8_t *data, uint16_t length);
 
 
 /* Add a friend without sending a friendrequest.
@@ -296,7 +296,7 @@ int32_t getfriend_id(const Messenger *m, const uint8_t *client_id);
  *  return 0 if success
  *  return -1 if failure
  */
-int getclient_id(Messenger *m, int32_t friendnumber, uint8_t *client_id);
+int getclient_id(const Messenger *m, int32_t friendnumber, uint8_t *client_id);
 
 /* Remove a friend.
  *
@@ -311,14 +311,14 @@ int m_delfriend(Messenger *m, int32_t friendnumber);
  *  return 0 if friend is not connected to us (Offline).
  *  return -1 on failure.
  */
-int m_get_friend_connectionstatus(Messenger *m, int32_t friendnumber);
+int m_get_friend_connectionstatus(const Messenger *m, int32_t friendnumber);
 
 /* Checks if there exists a friend with given friendnumber.
  *
  *  return 1 if friend exists.
  *  return 0 if friend doesn't exist.
  */
-int m_friend_exists(Messenger *m, int32_t friendnumber);
+int m_friend_exists(const Messenger *m, int32_t friendnumber);
 
 /* Send a text chat message to an online friend.
  *
@@ -344,8 +344,9 @@ uint32_t m_sendmessage_withid(Messenger *m, int32_t friendnumber, uint32_t theid
  *  m_sendaction_withid will send an action message with the id of your choosing,
  *  however we can generate an id for you by calling plain m_sendaction.
  */
-uint32_t m_sendaction(Messenger *m, int32_t friendnumber, uint8_t *action, uint32_t length);
-uint32_t m_sendaction_withid(Messenger *m, int32_t friendnumber, uint32_t theid, uint8_t *action, uint32_t length);
+uint32_t m_sendaction(Messenger *m, int32_t friendnumber, const uint8_t *action, uint32_t length);
+uint32_t m_sendaction_withid(const Messenger *m, int32_t friendnumber, uint32_t theid, const uint8_t *action,
+                             uint32_t length);
 
 /* Set the name and name_length of a friend.
  * name must be a string of maximum MAX_NAME_LENGTH length.
@@ -355,7 +356,7 @@ uint32_t m_sendaction_withid(Messenger *m, int32_t friendnumber, uint32_t theid,
  *  return 0 if success.
  *  return -1 if failure.
  */
-int setfriendname(Messenger *m, int32_t friendnumber, uint8_t *name, uint16_t length);
+int setfriendname(Messenger *m, int32_t friendnumber, const uint8_t *name, uint16_t length);
 
 /* Set our nickname.
  * name must be a string of maximum MAX_NAME_LENGTH length.
@@ -375,7 +376,7 @@ int setname(Messenger *m, const uint8_t *name, uint16_t length);
  *  return length of the name.
  *  return 0 on error.
  */
-uint16_t getself_name(Messenger *m, uint8_t *name);
+uint16_t getself_name(const Messenger *m, uint8_t *name);
 
 /* Get name of friendnumber and put it in name.
  * name needs to be a valid memory location with a size of at least MAX_NAME_LENGTH (128) bytes.
@@ -383,13 +384,13 @@ uint16_t getself_name(Messenger *m, uint8_t *name);
  *  return length of name if success.
  *  return -1 if failure.
  */
-int getname(Messenger *m, int32_t friendnumber, uint8_t *name);
+int getname(const Messenger *m, int32_t friendnumber, uint8_t *name);
 
 /*  return the length of name, including null on success.
  *  return -1 on failure.
  */
-int m_get_name_size(Messenger *m, int32_t friendnumber);
-int m_get_self_name_size(Messenger *m);
+int m_get_name_size(const Messenger *m, int32_t friendnumber);
+int m_get_self_name_size(const Messenger *m);
 
 /* Set our user status.
  * You are responsible for freeing status after.
@@ -403,8 +404,8 @@ int m_set_userstatus(Messenger *m, uint8_t status);
 /*  return the length of friendnumber's status message, including null on success.
  *  return -1 on failure.
  */
-int m_get_statusmessage_size(Messenger *m, int32_t friendnumber);
-int m_get_self_statusmessage_size(Messenger *m);
+int m_get_statusmessage_size(const Messenger *m, int32_t friendnumber);
+int m_get_self_statusmessage_size(const Messenger *m);
 
 /* Copy friendnumber's status message into buf, truncating if size is over maxlen.
  * Get the size you need to allocate from m_get_statusmessage_size.
@@ -413,21 +414,21 @@ int m_get_self_statusmessage_size(Messenger *m);
  * returns the length of the copied data on success
  * retruns -1 on failure.
  */
-int m_copy_statusmessage(Messenger *m, int32_t friendnumber, uint8_t *buf, uint32_t maxlen);
-int m_copy_self_statusmessage(Messenger *m, uint8_t *buf, uint32_t maxlen);
+int m_copy_statusmessage(const Messenger *m, int32_t friendnumber, uint8_t *buf, uint32_t maxlen);
+int m_copy_self_statusmessage(const Messenger *m, uint8_t *buf, uint32_t maxlen);
 
 /*  return one of USERSTATUS values.
  *  Values unknown to your application should be represented as USERSTATUS_NONE.
  *  As above, the self variant will return our own USERSTATUS.
  *  If friendnumber is invalid, this shall return USERSTATUS_INVALID.
  */
-uint8_t m_get_userstatus(Messenger *m, int32_t friendnumber);
-uint8_t m_get_self_userstatus(Messenger *m);
+uint8_t m_get_userstatus(const Messenger *m, int32_t friendnumber);
+uint8_t m_get_self_userstatus(const Messenger *m);
 
 /* returns timestamp of last time friendnumber was seen online, or 0 if never seen.
  * returns -1 on error.
  */
-uint64_t m_get_last_online(Messenger *m, int32_t friendnumber);
+uint64_t m_get_last_online(const Messenger *m, int32_t friendnumber);
 
 /* Set our typing status for a friend.
  * You are responsible for turning it on or off.
@@ -442,7 +443,7 @@ int m_set_usertyping(Messenger *m, int32_t friendnumber, uint8_t is_typing);
  * returns 0 if friend is not typing.
  * returns 1 if friend is typing.
  */
-uint8_t m_get_istyping(Messenger *m, int32_t friendnumber);
+uint8_t m_get_istyping(const Messenger *m, int32_t friendnumber);
 
 /* Sets whether we send read receipts for friendnumber.
  * This function is not lazy, and it will fail if yesno is not (0 or 1).
@@ -458,20 +459,20 @@ void m_callback_friendrequest(Messenger *m, void (*function)(Messenger *m, const
 /* Set the function that will be executed when a message from a friend is received.
  *  Function format is: function(int32_t friendnumber, uint8_t * message, uint32_t length)
  */
-void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata);
 
 /* Set the function that will be executed when an action from a friend is received.
  *  Function format is: function(int32_t friendnumber, uint8_t * action, uint32_t length)
  */
-void m_callback_action(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_action(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                        void *userdata);
 
 /* Set the callback for name changes.
  *  Function(int32_t friendnumber, uint8_t *newname, uint16_t length)
  *  You are not responsible for freeing newname.
  */
-void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                            void *userdata);
 
 /* Set the callback for status message changes.
@@ -479,7 +480,7 @@ void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int32_t,
  *
  *  You are not responsible for freeing newstatus
  */
-void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata);
 
 /* Set the callback for status type changes.
@@ -526,20 +527,21 @@ void m_callback_connectionstatus_internal_av(Messenger *m, void (*function)(Mess
  *
  *  Function(Messenger *m, int32_t friendnumber, uint8_t *group_public_key, void *userdata)
  */
-void m_callback_group_invite(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, void *), void *userdata);
+void m_callback_group_invite(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, void *),
+                             void *userdata);
 
 /* Set the callback for group messages.
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void m_callback_group_message(Messenger *m, void (*function)(Messenger *m, int, int, uint8_t *, uint16_t, void *),
+void m_callback_group_message(Messenger *m, void (*function)(Messenger *m, int, int, const uint8_t *, uint16_t, void *),
                               void *userdata);
 
 /* Set the callback for group actions.
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void m_callback_group_action(Messenger *m, void (*function)(Messenger *m, int, int, uint8_t *, uint16_t, void *),
+void m_callback_group_action(Messenger *m, void (*function)(Messenger *m, int, int, const uint8_t *, uint16_t, void *),
                              void *userdata);
 
 /* Set callback function for peer name list changes.
@@ -570,7 +572,7 @@ int del_groupchat(Messenger *m, int groupnumber);
  * return length of name if success
  * return -1 if failure
  */
-int m_group_peername(Messenger *m, int groupnumber, int peernumber, uint8_t *name);
+int m_group_peername(const Messenger *m, int groupnumber, int peernumber, uint8_t *name);
 
 /* invite friendnumber to groupnumber
  * return 0 on success
@@ -583,24 +585,24 @@ int invite_friend(Messenger *m, int32_t friendnumber, int groupnumber);
  * returns group number on success
  * returns -1 on failure.
  */
-int join_groupchat(Messenger *m, int32_t friendnumber, uint8_t *friend_group_public_key);
+int join_groupchat(Messenger *m, int32_t friendnumber, const uint8_t *friend_group_public_key);
 
 /* send a group message
  * return 0 on success
  * return -1 on failure
  */
-int group_message_send(Messenger *m, int groupnumber, uint8_t *message, uint32_t length);
+int group_message_send(const Messenger *m, int groupnumber, const uint8_t *message, uint32_t length);
 
 /* send a group action
  * return 0 on success
  * return -1 on failure
  */
-int group_action_send(Messenger *m, int groupnumber, uint8_t *action, uint32_t length);
+int group_action_send(const Messenger *m, int groupnumber, const uint8_t *action, uint32_t length);
 
 /* Return the number of peers in the group chat on success.
  * return -1 on failure
  */
-int group_number_peers(Messenger *m, int groupnumber);
+int group_number_peers(const Messenger *m, int groupnumber);
 
 /* List all the peers in the group chat.
  *
@@ -612,7 +614,8 @@ int group_number_peers(Messenger *m, int groupnumber);
  *
  * return -1 on failure.
  */
-int group_names(Messenger *m, int groupnumber, uint8_t names[][MAX_NICK_BYTES], uint16_t lengths[], uint16_t length);
+int group_names(const Messenger *m, int groupnumber, uint8_t names[][MAX_NICK_BYTES], uint16_t lengths[],
+                uint16_t length);
 
 /****************FILE SENDING*****************/
 
@@ -621,7 +624,7 @@ int group_names(Messenger *m, int groupnumber, uint8_t names[][MAX_NICK_BYTES],
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length, void *userdata)
  */
-void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint64_t, uint8_t *,
+void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint64_t, const uint8_t *,
                                uint16_t, void *), void *userdata);
 
 /* Set the callback for file control requests.
@@ -629,15 +632,15 @@ void callback_file_sendrequest(Messenger *m, void (*function)(Messenger *m, int3
  *  Function(Tox *tox, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t control_type, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void callback_file_control(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t, uint8_t, uint8_t *,
-                           uint16_t, void *), void *userdata);
+void callback_file_control(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t, uint8_t,
+                           const uint8_t *, uint16_t, void *), void *userdata);
 
 /* Set the callback for file data.
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, uint16_t length,
+void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, const uint8_t *, uint16_t length,
                         void *), void *userdata);
 
 /* Send a file send request.
@@ -645,15 +648,16 @@ void callback_file_data(Messenger *m, void (*function)(Messenger *m, int32_t, ui
  *  return 1 on success
  *  return 0 on failure
  */
-int file_sendrequest(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename,
-                     uint16_t filename_length);
+int file_sendrequest(const Messenger *m, int32_t friendnumber, uint8_t filenumber, uint64_t filesize,
+                     const uint8_t *filename, uint16_t filename_length);
 
 /* Send a file send request.
  * Maximum filename length is 255 bytes.
  *  return file number on success
  *  return -1 on failure
  */
-int new_filesender(Messenger *m, int32_t friendnumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length);
+int new_filesender(const Messenger *m, int32_t friendnumber, uint64_t filesize, const uint8_t *filename,
+                   uint16_t filename_length);
 
 /* Send a file control request.
  * send_receive is 0 if we want the control packet to target a sending file, 1 if it targets a receiving file.
@@ -661,15 +665,15 @@ int new_filesender(Messenger *m, int32_t friendnumber, uint64_t filesize, uint8_
  *  return 1 on success
  *  return 0 on failure
  */
-int file_control(Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
-                 uint8_t *data, uint16_t length);
+int file_control(const Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
+                 const uint8_t *data, uint16_t length);
 
 /* Send file data.
  *
  *  return 1 on success
  *  return 0 on failure
  */
-int file_data(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length);
+int file_data(const Messenger *m, int32_t friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length);
 
 /* Give the number of bytes left to be sent/received.
  *
@@ -678,7 +682,7 @@ int file_data(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t *d
  *  return number of bytes remaining to be sent/received on success
  *  return 0 on failure
  */
-uint64_t file_dataremaining(Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive);
+uint64_t file_dataremaining(const Messenger *m, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive);
 
 /*************** A/V related ******************/
 
@@ -686,7 +690,7 @@ uint64_t file_dataremaining(Messenger *m, int32_t friendnumber, uint8_t filenumb
  *
  *  Function(Messenger *m, int32_t friendnumber, uint8_t *data, uint16_t length, void *userdata)
  */
-void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t *, uint16_t, void *),
+void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t, const uint8_t *, uint16_t, void *),
                            void *userdata);
 
 /* Send an msi packet.
@@ -694,7 +698,7 @@ void m_callback_msi_packet(Messenger *m, void (*function)(Messenger *m, int32_t,
  *  return 1 on success
  *  return 0 on failure
  */
-int m_msi_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint16_t length);
+int m_msi_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint16_t length);
 
 /**********************************************/
 
@@ -704,14 +708,14 @@ int m_msi_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint16_t len
  * return 0 on success.
  */
 int custom_lossy_packet_registerhandler(Messenger *m, int32_t friendnumber, uint8_t byte,
-                                        int (*packet_handler_callback)(void *object, uint8_t *data, uint32_t len), void *object);
+                                        int (*packet_handler_callback)(void *object, const uint8_t *data, uint32_t len), void *object);
 
 /* High level function to send custom lossy packets.
  *
  * return -1 on failure.
  * return 0 on success.
  */
-int send_custom_lossy_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint32_t length);
+int send_custom_lossy_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint32_t length);
 
 
 /* Set handlers for custom lossless packets.
@@ -722,14 +726,14 @@ int send_custom_lossy_packet(Messenger *m, int32_t friendnumber, uint8_t *data,
  * return 0 on success.
  */
 int custom_lossless_packet_registerhandler(Messenger *m, int32_t friendnumber, uint8_t byte,
-        int (*packet_handler_callback)(void *object, uint8_t *data, uint32_t len), void *object);
+        int (*packet_handler_callback)(void *object, const uint8_t *data, uint32_t len), void *object);
 
 /* High level function to send custom lossless packets.
  *
  * return -1 on failure.
  * return 0 on success.
  */
-int send_custom_lossless_packet(Messenger *m, int32_t friendnumber, uint8_t *data, uint32_t length);
+int send_custom_lossless_packet(const Messenger *m, int32_t friendnumber, const uint8_t *data, uint32_t length);
 
 /**********************************************/
 /* Run this at startup.
@@ -756,28 +760,28 @@ uint32_t messenger_run_interval(Messenger *m);
 /* SAVING AND LOADING FUNCTIONS: */
 
 /* return size of the messenger data (for saving). */
-uint32_t messenger_size(Messenger *m);
+uint32_t messenger_size(const Messenger *m);
 
 /* Save the messenger in data (must be allocated memory of size Messenger_size()) */
-void messenger_save(Messenger *m, uint8_t *data);
+void messenger_save(const Messenger *m, uint8_t *data);
 
 /* Load the messenger from data of size length. */
-int messenger_load(Messenger *m, uint8_t *data, uint32_t length);
+int messenger_load(Messenger *m, const uint8_t *data, uint32_t length);
 
 /* Return the number of friends in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_friendlist. */
-uint32_t count_friendlist(Messenger *m);
+uint32_t count_friendlist(const Messenger *m);
 
 /* Return the number of online friends in the instance m. */
-uint32_t get_num_online_friends(Messenger *m);
+uint32_t get_num_online_friends(const Messenger *m);
 
 /* Copy a list of valid friend IDs into the array out_list.
  * If out_list is NULL, returns 0.
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t copy_friendlist(Messenger *m, int32_t *out_list, uint32_t list_size);
+uint32_t copy_friendlist(const Messenger *m, int32_t *out_list, uint32_t list_size);
 
 /* Allocate and return a list of valid friend id's. List must be freed by the
  * caller.
@@ -785,18 +789,18 @@ uint32_t copy_friendlist(Messenger *m, int32_t *out_list, uint32_t list_size);
  * retun 0 if success.
  * return -1 if failure.
  */
-int get_friendlist(Messenger *m, int **out_list, uint32_t *out_list_length);
+int get_friendlist(const Messenger *m, int **out_list, uint32_t *out_list_length);
 
 /* Return the number of chats in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_chatlist. */
-uint32_t count_chatlist(Messenger *m);
+uint32_t count_chatlist(const Messenger *m);
 
 /* Copy a list of valid chat IDs into the array out_list.
  * If out_list is NULL, returns 0.
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t copy_chatlist(Messenger *m, int *out_list, uint32_t list_size);
+uint32_t copy_chatlist(const Messenger *m, int *out_list, uint32_t list_size);
 
 #endif
diff --git a/toxcore/TCP_client.c b/toxcore/TCP_client.c
index e4845852..087188f7 100644
--- a/toxcore/TCP_client.c
+++ b/toxcore/TCP_client.c
@@ -65,7 +65,8 @@ static int connect_sock_to(sock_t sock, IP_Port ip_port)
 /* return 0 on success.
  * return -1 on failure.
  */
-static int generate_handshake(TCP_Client_Connection *TCP_conn, uint8_t *self_public_key, uint8_t *self_secret_key)
+static int generate_handshake(TCP_Client_Connection *TCP_conn, const uint8_t *self_public_key,
+                              const uint8_t *self_secret_key)
 {
     uint8_t plain[crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES];
     crypto_box_keypair(plain, TCP_conn->temp_secret_key);
@@ -90,7 +91,7 @@ static int generate_handshake(TCP_Client_Connection *TCP_conn, uint8_t *self_pub
  * return 0 on success.
  * return -1 on failure.
  */
-static int handle_handshake(TCP_Client_Connection *TCP_conn, uint8_t *data)
+static int handle_handshake(TCP_Client_Connection *TCP_conn, const uint8_t *data)
 {
     uint8_t plain[crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES];
     int len = decrypt_data_symmetric(TCP_conn->shared_key, data, data + crypto_box_NONCEBYTES,
@@ -137,7 +138,7 @@ static int send_pending_data(TCP_Client_Connection *con)
  * return 0 if could not send packet.
  * return -1 on failure (connection must be killed).
  */
-static int write_packet_TCP_secure_connection(TCP_Client_Connection *con, uint8_t *data, uint16_t length)
+static int write_packet_TCP_secure_connection(TCP_Client_Connection *con, const uint8_t *data, uint16_t length)
 {
     if (length + crypto_box_MACBYTES > MAX_PACKET_SIZE)
         return -1;
@@ -183,7 +184,7 @@ int send_routing_request(TCP_Client_Connection *con, uint8_t *public_key)
 }
 
 void routing_response_handler(TCP_Client_Connection *con, int (*response_callback)(void *object, uint8_t connection_id,
-                              uint8_t *public_key), void *object)
+                              const uint8_t *public_key), void *object)
 {
     con->response_callback = response_callback;
     con->response_callback_object = object;
@@ -200,7 +201,7 @@ void routing_status_handler(TCP_Client_Connection *con, int (*status_callback)(v
  * return 0 if could not send packet.
  * return -1 on failure.
  */
-int send_data(TCP_Client_Connection *con, uint8_t con_id, uint8_t *data, uint16_t length)
+int send_data(TCP_Client_Connection *con, uint8_t con_id, const uint8_t *data, uint16_t length)
 {
     if (con_id >= NUM_CLIENT_CONNECTIONS)
         return -1;
@@ -218,7 +219,7 @@ int send_data(TCP_Client_Connection *con, uint8_t con_id, uint8_t *data, uint16_
  * return 0 if could not send packet.
  * return -1 on failure.
  */
-int send_oob_packet(TCP_Client_Connection *con, uint8_t *public_key, uint8_t *data, uint16_t length)
+int send_oob_packet(TCP_Client_Connection *con, const uint8_t *public_key, const uint8_t *data, uint16_t length)
 {
     if (length == 0 || length > TCP_MAX_OOB_DATA_LENGTH)
         return -1;
@@ -251,14 +252,14 @@ int set_tcp_connection_number(TCP_Client_Connection *con, uint8_t con_id, uint32
 }
 
 void routing_data_handler(TCP_Client_Connection *con, int (*data_callback)(void *object, uint32_t number,
-                          uint8_t connection_id, uint8_t *data, uint16_t length), void *object)
+                          uint8_t connection_id, const uint8_t *data, uint16_t length), void *object)
 {
     con->data_callback = data_callback;
     con->data_callback_object = object;
 }
 
-void oob_data_handler(TCP_Client_Connection *con, int (*oob_data_callback)(void *object, uint8_t *public_key,
-                      uint8_t *data, uint16_t length), void *object)
+void oob_data_handler(TCP_Client_Connection *con, int (*oob_data_callback)(void *object, const uint8_t *public_key,
+                      const uint8_t *data, uint16_t length), void *object)
 {
     con->oob_data_callback = oob_data_callback;
     con->oob_data_callback_object = object;
@@ -318,7 +319,7 @@ int send_disconnect_request(TCP_Client_Connection *con, uint8_t con_id)
  * return 0 if could not send packet.
  * return -1 on failure (connection must be killed).
  */
-int send_onion_request(TCP_Client_Connection *con, uint8_t *data, uint16_t length)
+int send_onion_request(TCP_Client_Connection *con, const uint8_t *data, uint16_t length)
 {
     uint8_t packet[1 + length];
     packet[0] = TCP_PACKET_ONION_REQUEST;
@@ -326,7 +327,7 @@ int send_onion_request(TCP_Client_Connection *con, uint8_t *data, uint16_t lengt
     return write_packet_TCP_secure_connection(con, packet, sizeof(packet));
 }
 
-void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(void *object, uint8_t *data,
+void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(void *object, const uint8_t *data,
                             uint16_t length), void *object)
 {
     con->onion_callback = onion_callback;
@@ -335,8 +336,8 @@ void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(vo
 
 /* Create new TCP connection to ip_port/public_key
  */
-TCP_Client_Connection *new_TCP_connection(IP_Port ip_port, uint8_t *public_key, uint8_t *self_public_key,
-        uint8_t *self_secret_key)
+TCP_Client_Connection *new_TCP_connection(IP_Port ip_port, const uint8_t *public_key, const uint8_t *self_public_key,
+        const uint8_t *self_secret_key)
 {
     if (networking_at_startup() != 0) {
         return NULL;
@@ -388,7 +389,7 @@ TCP_Client_Connection *new_TCP_connection(IP_Port ip_port, uint8_t *public_key,
 /* return 0 on success
  * return -1 on failure
  */
-static int handle_TCP_packet(TCP_Client_Connection *conn, uint8_t *data, uint16_t length)
+static int handle_TCP_packet(TCP_Client_Connection *conn, const uint8_t *data, uint16_t length)
 {
     if (length <= 1)
         return -1;
diff --git a/toxcore/TCP_client.h b/toxcore/TCP_client.h
index afb95392..2622b4f7 100644
--- a/toxcore/TCP_client.h
+++ b/toxcore/TCP_client.h
@@ -64,23 +64,23 @@ typedef struct  {
         uint8_t public_key[crypto_box_PUBLICKEYBYTES];
         uint32_t number;
     } connections[NUM_CLIENT_CONNECTIONS];
-    int (*response_callback)(void *object, uint8_t connection_id, uint8_t *public_key);
+    int (*response_callback)(void *object, uint8_t connection_id, const uint8_t *public_key);
     void *response_callback_object;
     int (*status_callback)(void *object, uint32_t number, uint8_t connection_id, uint8_t status);
     void *status_callback_object;
-    int (*data_callback)(void *object, uint32_t number, uint8_t connection_id, uint8_t *data, uint16_t length);
+    int (*data_callback)(void *object, uint32_t number, uint8_t connection_id, const uint8_t *data, uint16_t length);
     void *data_callback_object;
-    int (*oob_data_callback)(void *object, uint8_t *public_key, uint8_t *data, uint16_t length);
+    int (*oob_data_callback)(void *object, const uint8_t *public_key, const uint8_t *data, uint16_t length);
     void *oob_data_callback_object;
 
-    int (*onion_callback)(void *object, uint8_t *data, uint16_t length);
+    int (*onion_callback)(void *object, const uint8_t *data, uint16_t length);
     void *onion_callback_object;
 } TCP_Client_Connection;
 
 /* Create new TCP connection to ip_port/public_key
  */
-TCP_Client_Connection *new_TCP_connection(IP_Port ip_port, uint8_t *public_key, uint8_t *self_public_key,
-        uint8_t *self_secret_key);
+TCP_Client_Connection *new_TCP_connection(IP_Port ip_port, const uint8_t *public_key, const uint8_t *self_public_key,
+        const uint8_t *self_secret_key);
 
 /* Run the TCP connection
  */
@@ -94,8 +94,8 @@ void kill_TCP_connection(TCP_Client_Connection *TCP_connection);
  * return 0 if could not send packet.
  * return -1 on failure (connection must be killed).
  */
-int send_onion_request(TCP_Client_Connection *con, uint8_t *data, uint16_t length);
-void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(void *object, uint8_t *data,
+int send_onion_request(TCP_Client_Connection *con, const uint8_t *data, uint16_t length);
+void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(void *object, const uint8_t *data,
                             uint16_t length), void *object);
 
 /* return 1 on success.
@@ -104,7 +104,7 @@ void onion_response_handler(TCP_Client_Connection *con, int (*onion_callback)(vo
  */
 int send_routing_request(TCP_Client_Connection *con, uint8_t *public_key);
 void routing_response_handler(TCP_Client_Connection *con, int (*response_callback)(void *object, uint8_t connection_id,
-                              uint8_t *public_key), void *object);
+                              const uint8_t *public_key), void *object);
 void routing_status_handler(TCP_Client_Connection *con, int (*status_callback)(void *object, uint32_t number,
                             uint8_t connection_id, uint8_t status), void *object);
 
@@ -127,17 +127,17 @@ int set_tcp_connection_number(TCP_Client_Connection *con, uint8_t con_id, uint32
  * return 0 if could not send packet.
  * return -1 on failure.
  */
-int send_data(TCP_Client_Connection *con, uint8_t con_id, uint8_t *data, uint16_t length);
+int send_data(TCP_Client_Connection *con, uint8_t con_id, const uint8_t *data, uint16_t length);
 void routing_data_handler(TCP_Client_Connection *con, int (*data_callback)(void *object, uint32_t number,
-                          uint8_t connection_id, uint8_t *data, uint16_t length), void *object);
+                          uint8_t connection_id, const uint8_t *data, uint16_t length), void *object);
 
 /* return 1 on success.
  * return 0 if could not send packet.
  * return -1 on failure.
  */
-int send_oob_packet(TCP_Client_Connection *con, uint8_t *public_key, uint8_t *data, uint16_t length);
-void oob_data_handler(TCP_Client_Connection *con, int (*oob_data_callback)(void *object, uint8_t *public_key,
-                      uint8_t *data, uint16_t length), void *object);
+int send_oob_packet(TCP_Client_Connection *con, const uint8_t *public_key, const uint8_t *data, uint16_t length);
+void oob_data_handler(TCP_Client_Connection *con, int (*oob_data_callback)(void *object, const uint8_t *public_key,
+                      const uint8_t *data, uint16_t length), void *object);
 
 
 #endif
diff --git a/toxcore/TCP_server.c b/toxcore/TCP_server.c
index 578784d0..7487ad4f 100644
--- a/toxcore/TCP_server.c
+++ b/toxcore/TCP_server.c
@@ -97,7 +97,7 @@ static int realloc_connection(TCP_Server *TCP_server, uint32_t num)
 /* return index corresponding to connection with peer on success
  * return -1 on failure.
  */
-static int get_TCP_connection_index(TCP_Server *TCP_server, uint8_t *public_key)
+static int get_TCP_connection_index(const TCP_Server *TCP_server, const uint8_t *public_key)
 {
     return bs_list_find(&TCP_server->accepted_key_list, public_key);
 }
@@ -110,7 +110,7 @@ static int kill_accepted(TCP_Server *TCP_server, int index);
  * return index on success
  * return -1 on failure
  */
-static int add_accepted(TCP_Server *TCP_server, TCP_Secure_Connection *con)
+static int add_accepted(TCP_Server *TCP_server, const TCP_Secure_Connection *con)
 {
     int index = get_TCP_connection_index(TCP_server, con->public_key);
 
@@ -249,7 +249,7 @@ int read_TCP_packet(sock_t sock, uint8_t *data, uint16_t length)
  * return 0 if could not read any packet.
  * return -1 on failure (connection must be killed).
  */
-int read_packet_TCP_secure_connection(sock_t sock, uint16_t *next_packet_length, uint8_t *shared_key,
+int read_packet_TCP_secure_connection(sock_t sock, uint16_t *next_packet_length, const uint8_t *shared_key,
                                       uint8_t *recv_nonce, uint8_t *data, uint16_t max_len)
 {
     if (*next_packet_length == 0) {
@@ -318,7 +318,7 @@ static int send_pending_data(TCP_Secure_Connection *con)
  * return 0 if could not send packet.
  * return -1 on failure (connection must be killed).
  */
-static int write_packet_TCP_secure_connection(TCP_Secure_Connection *con, uint8_t *data, uint16_t length)
+static int write_packet_TCP_secure_connection(TCP_Secure_Connection *con, const uint8_t *data, uint16_t length)
 {
     if (length + crypto_box_MACBYTES > MAX_PACKET_SIZE)
         return -1;
@@ -389,7 +389,8 @@ static int kill_accepted(TCP_Server *TCP_server, int index)
 /* return 1 if everything went well.
  * return -1 if the connection must be killed.
  */
-static int handle_TCP_handshake(TCP_Secure_Connection *con, uint8_t *data, uint16_t length, uint8_t *self_secret_key)
+static int handle_TCP_handshake(TCP_Secure_Connection *con, const uint8_t *data, uint16_t length,
+                                const uint8_t *self_secret_key)
 {
     if (length != TCP_CLIENT_HANDSHAKE_SIZE)
         return -1;
@@ -435,7 +436,7 @@ static int handle_TCP_handshake(TCP_Secure_Connection *con, uint8_t *data, uint1
  * return 0 if we didn't get it yet.
  * return -1 if the connection must be killed.
  */
-static int read_connection_handshake(TCP_Secure_Connection *con, uint8_t *self_secret_key)
+static int read_connection_handshake(TCP_Secure_Connection *con, const uint8_t *self_secret_key)
 {
     uint8_t data[TCP_CLIENT_HANDSHAKE_SIZE];
     int len = 0;
@@ -451,7 +452,7 @@ static int read_connection_handshake(TCP_Secure_Connection *con, uint8_t *self_s
  * return 0 if could not send packet.
  * return -1 on failure (connection must be killed).
  */
-static int send_routing_response(TCP_Secure_Connection *con, uint8_t rpid, uint8_t *public_key)
+static int send_routing_response(TCP_Secure_Connection *con, uint8_t rpid, const uint8_t *public_key)
 {
     uint8_t data[1 + 1 + crypto_box_PUBLICKEYBYTES];
     data[0] = TCP_PACKET_ROUTING_RESPONSE;
@@ -484,7 +485,7 @@ static int send_disconnect_notification(TCP_Secure_Connection *con, uint8_t id)
 /* return 0 on success.
  * return -1 on failure (connection must be killed).
  */
-static int handle_TCP_routing_req(TCP_Server *TCP_server, uint32_t con_id, uint8_t *public_key)
+static int handle_TCP_routing_req(TCP_Server *TCP_server, uint32_t con_id, const uint8_t *public_key)
 {
     uint32_t i;
     uint32_t index = ~0;
@@ -562,7 +563,7 @@ static int handle_TCP_routing_req(TCP_Server *TCP_server, uint32_t con_id, uint8
 /* return 0 on success.
  * return -1 on failure (connection must be killed).
  */
-static int handle_TCP_oob_send(TCP_Server *TCP_server, uint32_t con_id, uint8_t *public_key, uint8_t *data,
+static int handle_TCP_oob_send(TCP_Server *TCP_server, uint32_t con_id, const uint8_t *public_key, const uint8_t *data,
                                uint16_t length)
 {
     if (length == 0 || length > TCP_MAX_OOB_DATA_LENGTH)
@@ -645,7 +646,7 @@ static int handle_onion_recv_1(void *object, IP_Port dest, const uint8_t *data,
 /* return 0 on success
  * return -1 on failure
  */
-static int handle_TCP_packet(TCP_Server *TCP_server, uint32_t con_id, uint8_t *data, uint16_t length)
+static int handle_TCP_packet(TCP_Server *TCP_server, uint32_t con_id, const uint8_t *data, uint16_t length)
 {
     if (length == 0)
         return -1;
@@ -764,7 +765,8 @@ static int handle_TCP_packet(TCP_Server *TCP_server, uint32_t con_id, uint8_t *d
 }
 
 
-static int confirm_TCP_connection(TCP_Server *TCP_server, TCP_Secure_Connection *con, uint8_t *data, uint16_t length)
+static int confirm_TCP_connection(TCP_Server *TCP_server, TCP_Secure_Connection *con, const uint8_t *data,
+                                  uint16_t length)
 {
     int index = add_accepted(TCP_server, con);
 
@@ -838,8 +840,8 @@ static sock_t new_listening_TCP_socket(int family, uint16_t port)
     return sock;
 }
 
-TCP_Server *new_TCP_server(uint8_t ipv6_enabled, uint16_t num_sockets, uint16_t *ports, uint8_t *public_key,
-                           uint8_t *secret_key, Onion *onion)
+TCP_Server *new_TCP_server(uint8_t ipv6_enabled, uint16_t num_sockets, const uint16_t *ports, const uint8_t *public_key,
+                           const uint8_t *secret_key, Onion *onion)
 {
     if (num_sockets == 0 || ports == NULL)
         return NULL;
diff --git a/toxcore/TCP_server.h b/toxcore/TCP_server.h
index 40984778..def0a978 100644
--- a/toxcore/TCP_server.h
+++ b/toxcore/TCP_server.h
@@ -133,8 +133,8 @@ typedef struct {
 
 /* Create new TCP server instance.
  */
-TCP_Server *new_TCP_server(uint8_t ipv6_enabled, uint16_t num_sockets, uint16_t *ports, uint8_t *public_key,
-                           uint8_t *secret_key, Onion *onion);
+TCP_Server *new_TCP_server(uint8_t ipv6_enabled, uint16_t num_sockets, const uint16_t *ports, const uint8_t *public_key,
+                           const uint8_t *secret_key, Onion *onion);
 
 /* Run the TCP_server
  */
@@ -164,7 +164,7 @@ int read_TCP_packet(sock_t sock, uint8_t *data, uint16_t length);
  * return 0 if could not read any packet.
  * return -1 on failure (connection must be killed).
  */
-int read_packet_TCP_secure_connection(sock_t sock, uint16_t *next_packet_length, uint8_t *shared_key,
+int read_packet_TCP_secure_connection(sock_t sock, uint16_t *next_packet_length, const uint8_t *shared_key,
                                       uint8_t *recv_nonce, uint8_t *data, uint16_t max_len);
 
 
diff --git a/toxcore/net_crypto.c b/toxcore/net_crypto.c
index 8d598469..e0319f34 100644
--- a/toxcore/net_crypto.c
+++ b/toxcore/net_crypto.c
@@ -32,7 +32,7 @@
 #include "util.h"
 #include "math.h"
 
-static uint8_t crypt_connection_id_not_valid(Net_Crypto *c, int crypt_connection_id)
+static uint8_t crypt_connection_id_not_valid(const Net_Crypto *c, int crypt_connection_id)
 {
     return (uint32_t)crypt_connection_id >= c->crypto_connections_length;
 }
@@ -70,7 +70,7 @@ static int is_alive(uint8_t status)
  * return -1 on failure.
  * return COOKIE_REQUEST_LENGTH on success.
  */
-static int create_cookie_request(Net_Crypto *c, uint8_t *packet, uint8_t *dht_public_key, uint64_t number,
+static int create_cookie_request(const Net_Crypto *c, uint8_t *packet, uint8_t *dht_public_key, uint64_t number,
                                  uint8_t *shared_key)
 {
     uint8_t plain[COOKIE_REQUEST_PLAIN_LENGTH];
@@ -100,7 +100,7 @@ static int create_cookie_request(Net_Crypto *c, uint8_t *packet, uint8_t *dht_pu
  * return -1 on failure.
  * return 0 on success.
  */
-static int create_cookie(uint8_t *cookie, uint8_t *bytes, uint8_t *encryption_key)
+static int create_cookie(uint8_t *cookie, const uint8_t *bytes, const uint8_t *encryption_key)
 {
     uint8_t contents[COOKIE_CONTENTS_LENGTH];
     uint64_t temp_time = unix_time();
@@ -148,8 +148,8 @@ static int open_cookie(uint8_t *bytes, const uint8_t *cookie, const uint8_t *enc
  * return -1 on failure.
  * return COOKIE_RESPONSE_LENGTH on success.
  */
-static int create_cookie_response(Net_Crypto *c, uint8_t *packet, uint8_t *request_plain, uint8_t *shared_key,
-                                  uint8_t *dht_public_key)
+static int create_cookie_response(const Net_Crypto *c, uint8_t *packet, const uint8_t *request_plain,
+                                  const uint8_t *shared_key, const uint8_t *dht_public_key)
 {
     uint8_t cookie_plain[COOKIE_DATA_LENGTH];
     memcpy(cookie_plain, request_plain, crypto_box_PUBLICKEYBYTES);
@@ -177,8 +177,8 @@ static int create_cookie_response(Net_Crypto *c, uint8_t *packet, uint8_t *reque
  * return -1 on failure.
  * return 0 on success.
  */
-static int handle_cookie_request(Net_Crypto *c, uint8_t *request_plain, uint8_t *shared_key, uint8_t *dht_public_key,
-                                 const uint8_t *packet, uint16_t length)
+static int handle_cookie_request(const Net_Crypto *c, uint8_t *request_plain, uint8_t *shared_key,
+                                 uint8_t *dht_public_key, const uint8_t *packet, uint16_t length)
 {
     if (length != COOKIE_REQUEST_LENGTH)
         return -1;
@@ -220,8 +220,8 @@ static int udp_handle_cookie_request(void *object, IP_Port source, const uint8_t
 
 /* Handle the cookie request packet (for TCP)
  */
-static int tcp_handle_cookie_request(Net_Crypto *c, TCP_Client_Connection *TCP_con, uint8_t conn_id, uint8_t *packet,
-                                     uint32_t length)
+static int tcp_handle_cookie_request(const Net_Crypto *c, TCP_Client_Connection *TCP_con, uint8_t conn_id,
+                                     const uint8_t *packet, uint32_t length)
 {
     uint8_t request_plain[COOKIE_REQUEST_PLAIN_LENGTH];
     uint8_t shared_key[crypto_box_BEFORENMBYTES];
@@ -243,8 +243,8 @@ static int tcp_handle_cookie_request(Net_Crypto *c, TCP_Client_Connection *TCP_c
 
 /* Handle the cookie request packet (for TCP oob packets)
  */
-static int tcp_oob_handle_cookie_request(Net_Crypto *c, TCP_Client_Connection *TCP_con, uint8_t *dht_public_key,
-        uint8_t *packet, uint32_t length)
+static int tcp_oob_handle_cookie_request(const Net_Crypto *c, TCP_Client_Connection *TCP_con,
+        const uint8_t *dht_public_key, const uint8_t *packet, uint32_t length)
 {
     uint8_t request_plain[COOKIE_REQUEST_PLAIN_LENGTH];
     uint8_t shared_key[crypto_box_BEFORENMBYTES];
@@ -302,8 +302,8 @@ static int handle_cookie_response(uint8_t *cookie, uint64_t *number, const uint8
  * return -1 on failure.
  * return HANDSHAKE_PACKET_LENGTH on success.
  */
-static int create_crypto_handshake(Net_Crypto *c, uint8_t *packet, uint8_t *cookie, uint8_t *nonce, uint8_t *session_pk,
-                                   uint8_t *peer_real_pk, uint8_t *peer_dht_pubkey)
+static int create_crypto_handshake(const Net_Crypto *c, uint8_t *packet, const uint8_t *cookie, const uint8_t *nonce,
+                                   const uint8_t *session_pk, const uint8_t *peer_real_pk, const uint8_t *peer_dht_pubkey)
 {
     uint8_t plain[crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES + crypto_hash_sha512_BYTES + COOKIE_LENGTH];
     memcpy(plain, nonce, crypto_box_NONCEBYTES);
@@ -348,8 +348,8 @@ static int create_crypto_handshake(Net_Crypto *c, uint8_t *packet, uint8_t *cook
  * return -1 on failure.
  * return 0 on success.
  */
-static int handle_crypto_handshake(Net_Crypto *c, uint8_t *nonce, uint8_t *session_pk, uint8_t *peer_real_pk,
-                                   uint8_t *dht_public_key, uint8_t *cookie, const uint8_t *packet, uint32_t length, uint8_t *expected_real_pk)
+static int handle_crypto_handshake(const Net_Crypto *c, uint8_t *nonce, uint8_t *session_pk, uint8_t *peer_real_pk,
+                                   uint8_t *dht_public_key, uint8_t *cookie, const uint8_t *packet, uint32_t length, const uint8_t *expected_real_pk)
 {
     if (length != HANDSHAKE_PACKET_LENGTH)
         return -1;
@@ -386,7 +386,7 @@ static int handle_crypto_handshake(Net_Crypto *c, uint8_t *nonce, uint8_t *sessi
 }
 
 
-static Crypto_Connection *get_crypto_connection(Net_Crypto *c, int crypt_connection_id)
+static Crypto_Connection *get_crypto_connection(const Net_Crypto *c, int crypt_connection_id)
 {
     if (crypt_connection_id_not_valid(c, crypt_connection_id))
         return 0;
@@ -400,7 +400,7 @@ static Crypto_Connection *get_crypto_connection(Net_Crypto *c, int crypt_connect
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_packet_to(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint16_t length)
+static int send_packet_to(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint16_t length)
 {
 //TODO TCP, etc...
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
@@ -456,7 +456,7 @@ static int send_packet_to(Net_Crypto *c, int crypt_connection_id, uint8_t *data,
 /* Return number of packets in array
  * Note that holes are counted too.
  */
-static uint32_t num_packets_array(Packets_Array *array)
+static uint32_t num_packets_array(const Packets_Array *array)
 {
     return array->buffer_end - array->buffer_start;
 }
@@ -466,7 +466,7 @@ static uint32_t num_packets_array(Packets_Array *array)
  * return -1 on failure.
  * return 0 on success.
  */
-static int add_data_to_buffer(Packets_Array *array, uint32_t number, Packet_Data *data)
+static int add_data_to_buffer(Packets_Array *array, uint32_t number, const Packet_Data *data)
 {
     if (number - array->buffer_start > CRYPTO_PACKET_BUFFER_SIZE)
         return -1;
@@ -496,7 +496,7 @@ static int add_data_to_buffer(Packets_Array *array, uint32_t number, Packet_Data
  * return 0 if data at number is empty.
  * return 1 if data pointer was put in data.
  */
-static int get_data_pointer(Packets_Array *array, Packet_Data **data, uint32_t number)
+static int get_data_pointer(const Packets_Array *array, Packet_Data **data, uint32_t number)
 {
     uint32_t num_spots = array->buffer_end - array->buffer_start;
 
@@ -517,7 +517,7 @@ static int get_data_pointer(Packets_Array *array, Packet_Data **data, uint32_t n
  * return -1 on failure.
  * return packet number on success.
  */
-static int64_t add_data_end_of_buffer(Packets_Array *array, Packet_Data *data)
+static int64_t add_data_end_of_buffer(Packets_Array *array, const Packet_Data *data)
 {
     if (num_packets_array(array) >= CRYPTO_PACKET_BUFFER_SIZE)
         return -1;
@@ -607,7 +607,7 @@ static int set_buffer_end(Packets_Array *array, uint32_t number)
  * return -1 on failure.
  * return length of packet on success.
  */
-static int generate_request_packet(uint8_t *data, uint16_t length, Packets_Array *recv_array)
+static int generate_request_packet(uint8_t *data, uint16_t length, const Packets_Array *recv_array)
 {
     if (length == 0)
         return -1;
@@ -656,7 +656,7 @@ static int generate_request_packet(uint8_t *data, uint16_t length, Packets_Array
  * return -1 on failure.
  * return number of requested packets on success.
  */
-static int handle_request_packet(Packets_Array *send_array, uint8_t *data, uint16_t length)
+static int handle_request_packet(Packets_Array *send_array, const uint8_t *data, uint16_t length)
 {
     if (length < 1)
         return -1;
@@ -718,7 +718,7 @@ static int handle_request_packet(Packets_Array *send_array, uint8_t *data, uint1
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_data_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint16_t length)
+static int send_data_packet(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint16_t length)
 {
     if (length == 0 || length + (1 + sizeof(uint16_t) + crypto_box_MACBYTES) > MAX_CRYPTO_PACKET_SIZE)
         return -1;
@@ -750,8 +750,8 @@ static int send_data_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *dat
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_data_packet_helper(Net_Crypto *c, int crypt_connection_id, uint32_t buffer_start, uint32_t num,
-                                   uint8_t *data, uint32_t length)
+static int send_data_packet_helper(const Net_Crypto *c, int crypt_connection_id, uint32_t buffer_start, uint32_t num,
+                                   const uint8_t *data, uint32_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_DATA_SIZE)
         return -1;
@@ -771,7 +771,7 @@ static int send_data_packet_helper(Net_Crypto *c, int crypt_connection_id, uint3
 /*  return -1 if data could not be put in packet queue.
  *  return positive packet number if data was put into the queue.
  */
-static int64_t send_lossless_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint32_t length)
+static int64_t send_lossless_packet(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_DATA_SIZE)
         return -1;
@@ -781,8 +781,29 @@ static int64_t send_lossless_packet(Net_Crypto *c, int crypt_connection_id, uint
     if (conn == 0)
         return -1;
 
+    uint64_t temp_time = current_time_monotonic();
+
+    /* If last packet send failed, try to send packet again.
+       If sending it fails we won't be able to send the new packet. */
+    if (conn->maximum_speed_reached) {
+        Packet_Data *dt = NULL;
+        uint32_t packet_num = conn->send_array.buffer_end - 1;
+        int ret = get_data_pointer(&conn->send_array, &dt, packet_num);
+
+        if (ret == 1) {
+            if (!dt->time) {
+                if (send_data_packet_helper(c, crypt_connection_id, conn->recv_array.buffer_start, packet_num, dt->data,
+                                            dt->length) != 0) {
+                    return -1;
+                }
+
+                dt->time = temp_time;
+            }
+        }
+    }
+
     Packet_Data dt;
-    dt.time = current_time_monotonic();
+    dt.time = temp_time;
     dt.length = length;
     memcpy(dt.data, data, length);
     int64_t packet_num = add_data_end_of_buffer(&conn->send_array, &dt);
@@ -790,8 +811,15 @@ static int64_t send_lossless_packet(Net_Crypto *c, int crypt_connection_id, uint
     if (packet_num == -1)
         return -1;
 
-    if (send_data_packet_helper(c, crypt_connection_id, conn->recv_array.buffer_start, packet_num, data, length) != 0)
+    conn->maximum_speed_reached = 0;
+
+    if (send_data_packet_helper(c, crypt_connection_id, conn->recv_array.buffer_start, packet_num, data, length) != 0) {
+        Packet_Data *dt1 = NULL;
+        get_data_pointer(&conn->send_array, &dt1, packet_num);
+        dt1->time = 0;
+        conn->maximum_speed_reached = 1;
         fprintf(stderr, "send_data_packet failed\n");
+    }
 
     return packet_num;
 }
@@ -799,7 +827,7 @@ static int64_t send_lossless_packet(Net_Crypto *c, int crypt_connection_id, uint
 /* Get the lowest 2 bytes from the nonce and convert
  * them to host byte format before returning them.
  */
-static uint16_t get_nonce_uint16(uint8_t *nonce)
+static uint16_t get_nonce_uint16(const uint8_t *nonce)
 {
     uint16_t num;
     memcpy(&num, nonce + (crypto_box_NONCEBYTES - sizeof(uint16_t)), sizeof(uint16_t));
@@ -815,7 +843,7 @@ static uint16_t get_nonce_uint16(uint8_t *nonce)
  * return -1 on failure.
  * return length of data on success.
  */
-static int handle_data_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *data, const uint8_t *packet,
+static int handle_data_packet(const Net_Crypto *c, int crypt_connection_id, uint8_t *data, const uint8_t *packet,
                               uint16_t length)
 {
     if (length <= (1 + sizeof(uint16_t) + crypto_box_MACBYTES) || length > MAX_CRYPTO_PACKET_SIZE)
@@ -852,7 +880,7 @@ static int handle_data_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *d
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_request_packet(Net_Crypto *c, int crypt_connection_id)
+static int send_request_packet(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -874,7 +902,7 @@ static int send_request_packet(Net_Crypto *c, int crypt_connection_id)
  * return -1 on failure.
  * return number of packets sent on success.
  */
-static int send_requested_packets(Net_Crypto *c, int crypt_connection_id, uint16_t max_num)
+static int send_requested_packets(const Net_Crypto *c, int crypt_connection_id, uint16_t max_num)
 {
     if (max_num == 0)
         return -1;
@@ -920,7 +948,7 @@ static int send_requested_packets(Net_Crypto *c, int crypt_connection_id, uint16
  * return -1 on failure.
  * return 0 on success.
  */
-static int new_temp_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *packet, uint16_t length)
+static int new_temp_packet(const Net_Crypto *c, int crypt_connection_id, const uint8_t *packet, uint16_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_PACKET_SIZE)
         return -1;
@@ -951,7 +979,7 @@ static int new_temp_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *pack
  * return -1 on failure.
  * return 0 on success.
  */
-static int clear_temp_packet(Net_Crypto *c, int crypt_connection_id)
+static int clear_temp_packet(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -974,7 +1002,7 @@ static int clear_temp_packet(Net_Crypto *c, int crypt_connection_id)
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_temp_packet(Net_Crypto *c, int crypt_connection_id)
+static int send_temp_packet(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -998,7 +1026,8 @@ static int send_temp_packet(Net_Crypto *c, int crypt_connection_id)
  * return -1 on failure.
  * return 0 on success.
  */
-static int create_send_handshake(Net_Crypto *c, int crypt_connection_id, uint8_t *cookie, uint8_t *dht_public_key)
+static int create_send_handshake(const Net_Crypto *c, int crypt_connection_id, const uint8_t *cookie,
+                                 const uint8_t *dht_public_key)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1023,7 +1052,7 @@ static int create_send_handshake(Net_Crypto *c, int crypt_connection_id, uint8_t
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_kill_packet(Net_Crypto *c, int crypt_connection_id)
+static int send_kill_packet(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1040,7 +1069,8 @@ static int send_kill_packet(Net_Crypto *c, int crypt_connection_id)
  * return -1 on failure.
  * return 0 on success.
  */
-static int handle_data_packet_helper(Net_Crypto *c, int crypt_connection_id, const uint8_t *packet, uint16_t length)
+static int handle_data_packet_helper(const Net_Crypto *c, int crypt_connection_id, const uint8_t *packet,
+                                     uint16_t length)
 {
     if (length > MAX_CRYPTO_PACKET_SIZE || length <= CRYPTO_DATA_PACKET_MIN_SIZE)
         return -1;
@@ -1289,7 +1319,7 @@ static int wipe_crypto_connection(Net_Crypto *c, int crypt_connection_id)
  *  return -1 if there are no connections like we are looking for.
  *  return id if it found it.
  */
-static int getcryptconnection_id(Net_Crypto *c, uint8_t *public_key)
+static int getcryptconnection_id(const Net_Crypto *c, const uint8_t *public_key)
 {
     uint32_t i;
 
@@ -1307,7 +1337,7 @@ static int getcryptconnection_id(Net_Crypto *c, uint8_t *public_key)
  *  return -1 if there are no connections like we are looking for.
  *  return id if it found it.
  */
-static int getcryptconnection_id_dht_pubkey(Net_Crypto *c, uint8_t *dht_public_key)
+static int getcryptconnection_id_dht_pubkey(const Net_Crypto *c, const uint8_t *dht_public_key)
 {
     uint32_t i;
 
@@ -1465,7 +1495,7 @@ int accept_crypto_connection(Net_Crypto *c, New_Connection *n_c)
  * return -1 on failure.
  * return connection id on success.
  */
-int new_crypto_connection(Net_Crypto *c, uint8_t *real_public_key)
+int new_crypto_connection(Net_Crypto *c, const uint8_t *real_public_key)
 {
     int crypt_connection_id = getcryptconnection_id(c, real_public_key);
 
@@ -1495,7 +1525,7 @@ int new_crypto_connection(Net_Crypto *c, uint8_t *real_public_key)
  * return -1 on failure.
  * return 0 on success.
  */
-static int disconnect_peer_tcp(Net_Crypto *c, int crypt_connection_id)
+static int disconnect_peer_tcp(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1520,7 +1550,7 @@ static int disconnect_peer_tcp(Net_Crypto *c, int crypt_connection_id)
  * return -1 on failure.
  * return 0 on success.
  */
-static int connect_peer_tcp(Net_Crypto *c, int crypt_connection_id)
+static int connect_peer_tcp(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1545,7 +1575,7 @@ static int connect_peer_tcp(Net_Crypto *c, int crypt_connection_id)
  * return 0 on failure (no key copied).
  * return timestamp on success (key copied).
  */
-uint64_t get_connection_dht_key(Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key)
+uint64_t get_connection_dht_key(const Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1567,7 +1597,8 @@ uint64_t get_connection_dht_key(Net_Crypto *c, int crypt_connection_id, uint8_t
  * return -1 on failure.
  * return 0 on success.
  */
-int set_connection_dht_public_key(Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key, uint64_t timestamp)
+int set_connection_dht_public_key(const Net_Crypto *c, int crypt_connection_id, const uint8_t *dht_public_key,
+                                  uint64_t timestamp)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1628,7 +1659,7 @@ int set_direct_ip_port(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port)
     return -1;
 }
 
-static int tcp_response_callback(void *object, uint8_t connection_id, uint8_t *public_key)
+static int tcp_response_callback(void *object, uint8_t connection_id, const uint8_t *public_key)
 {
     TCP_Client_Connection *TCP_con = object;
     Net_Crypto *c = TCP_con->net_crypto_pointer;
@@ -1695,7 +1726,7 @@ static int tcp_status_callback(void *object, uint32_t number, uint8_t connection
     return 0;
 }
 
-static int tcp_data_callback(void *object, uint32_t number, uint8_t connection_id, uint8_t *data, uint16_t length)
+static int tcp_data_callback(void *object, uint32_t number, uint8_t connection_id, const uint8_t *data, uint16_t length)
 {
 
     if (length == 0)
@@ -1720,7 +1751,7 @@ static int tcp_data_callback(void *object, uint32_t number, uint8_t connection_i
     return 0;
 }
 
-static int tcp_oob_callback(void *object, uint8_t *public_key, uint8_t *data, uint16_t length)
+static int tcp_oob_callback(void *object, const uint8_t *public_key, const uint8_t *data, uint16_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_PACKET_SIZE)
         return -1;
@@ -1762,7 +1793,7 @@ static int tcp_oob_callback(void *object, uint8_t *public_key, uint8_t *data, ui
  * return -1 if it can't.
  * return 0 if it can.
  */
-static int tcp_connection_check(Net_Crypto *c, uint8_t *public_key)
+static int tcp_connection_check(const Net_Crypto *c, const uint8_t *public_key)
 {
     uint32_t i;
 
@@ -1797,7 +1828,7 @@ static int tcp_connection_check(Net_Crypto *c, uint8_t *public_key)
  * return 0 if it was added.
  * return -1 if it wasn't.
  */
-int add_tcp_relay_peer(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port, uint8_t *public_key)
+int add_tcp_relay_peer(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port, const uint8_t *public_key)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -1850,7 +1881,7 @@ int add_tcp_relay_peer(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port,
  * return 0 if it was added.
  * return -1 if it wasn't.
  */
-int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, uint8_t *public_key)
+int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, const uint8_t *public_key)
 {
     if (ip_port.ip.family == TCP_INET) {
         ip_port.ip.family = AF_INET;
@@ -1882,7 +1913,7 @@ int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, uint8_t *public_key)
  * return number of relays copied to tcp_relays on success.
  * return 0 on failure.
  */
-unsigned int copy_connected_tcp_relays(Net_Crypto *c, Node_format *tcp_relays, uint16_t num)
+unsigned int copy_connected_tcp_relays(const Net_Crypto *c, Node_format *tcp_relays, uint16_t num)
 {
     if (num == 0)
         return 0;
@@ -2046,8 +2077,8 @@ static void clear_disconnected_tcp(Net_Crypto *c)
  * return -1 on failure.
  * return 0 on success.
  */
-int connection_status_handler(Net_Crypto *c, int crypt_connection_id, int (*connection_status_callback)(void *object,
-                              int id, uint8_t status), void *object, int id)
+int connection_status_handler(const Net_Crypto *c, int crypt_connection_id,
+                              int (*connection_status_callback)(void *object, int id, uint8_t status), void *object, int id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -2068,7 +2099,7 @@ int connection_status_handler(Net_Crypto *c, int crypt_connection_id, int (*conn
  * return -1 on failure.
  * return 0 on success.
  */
-int connection_data_handler(Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
+int connection_data_handler(const Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
                             int id, uint8_t *data, uint16_t length), void *object, int id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
@@ -2091,7 +2122,7 @@ int connection_data_handler(Net_Crypto *c, int crypt_connection_id, int (*connec
  * return 0 on success.
  */
 int connection_lossy_data_handler(Net_Crypto *c, int crypt_connection_id,
-                                  int (*connection_lossy_data_callback)(void *object, int id, uint8_t *data, uint16_t length), void *object, int id)
+                                  int (*connection_lossy_data_callback)(void *object, int id, const uint8_t *data, uint16_t length), void *object, int id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -2109,7 +2140,7 @@ int connection_lossy_data_handler(Net_Crypto *c, int crypt_connection_id,
  * return -1 on failure.
  * return connection id on success.
  */
-static int crypto_id_ip_port(Net_Crypto *c, IP_Port ip_port)
+static int crypto_id_ip_port(const Net_Crypto *c, IP_Port ip_port)
 {
     return bs_list_find(&c->ip_port_list, &ip_port);
 }
@@ -2345,7 +2376,7 @@ static void send_crypto_packets(Net_Crypto *c)
 /* returns the number of packet slots left in the sendbuffer.
  * return 0 if failure.
  */
-uint32_t crypto_num_free_sendqueue_slots(Net_Crypto *c, int crypt_connection_id)
+uint32_t crypto_num_free_sendqueue_slots(const Net_Crypto *c, int crypt_connection_id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -2362,7 +2393,7 @@ uint32_t crypto_num_free_sendqueue_slots(Net_Crypto *c, int crypt_connection_id)
  *
  * The first byte of data must be in the CRYPTO_RESERVED_PACKETS to PACKET_ID_LOSSY_RANGE_START range.
  */
-int64_t write_cryptpacket(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint32_t length)
+int64_t write_cryptpacket(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0)
         return -1;
@@ -2399,7 +2430,7 @@ int64_t write_cryptpacket(Net_Crypto *c, int crypt_connection_id, uint8_t *data,
  *
  * Sends a lossy cryptopacket. (first byte must in the PACKET_ID_LOSSY_RANGE_*)
  */
-int send_lossy_cryptpacket(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint32_t length)
+int send_lossy_cryptpacket(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_DATA_SIZE)
         return -1;
@@ -2441,7 +2472,7 @@ int crypto_kill(Net_Crypto *c, int crypt_connection_id)
  *
  * sets direct_connected to 1 if connection connects directly to other, 0 if it isn't.
  */
-unsigned int crypto_connection_status(Net_Crypto *c, int crypt_connection_id, uint8_t *direct_connected)
+unsigned int crypto_connection_status(const Net_Crypto *c, int crypt_connection_id, uint8_t *direct_connected)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
@@ -2464,7 +2495,7 @@ void new_keys(Net_Crypto *c)
 /* Save the public and private keys to the keys array.
  * Length must be crypto_box_PUBLICKEYBYTES + crypto_box_SECRETKEYBYTES.
  */
-void save_keys(Net_Crypto *c, uint8_t *keys)
+void save_keys(const Net_Crypto *c, uint8_t *keys)
 {
     memcpy(keys, c->self_public_key, crypto_box_PUBLICKEYBYTES);
     memcpy(keys + crypto_box_PUBLICKEYBYTES, c->self_secret_key, crypto_box_SECRETKEYBYTES);
@@ -2552,7 +2583,7 @@ static void kill_timedout(Net_Crypto *c)
 
 /* return the optimal interval in ms for running do_net_crypto.
  */
-uint32_t crypto_run_interval(Net_Crypto *c)
+uint32_t crypto_run_interval(const Net_Crypto *c)
 {
     return c->current_sleep_time;
 }
diff --git a/toxcore/net_crypto.h b/toxcore/net_crypto.h
index d30d5a63..4fed0000 100644
--- a/toxcore/net_crypto.h
+++ b/toxcore/net_crypto.h
@@ -129,7 +129,7 @@ typedef struct {
     void *connection_data_callback_object;
     int connection_data_callback_id;
 
-    int (*connection_lossy_data_callback)(void *object, int id, uint8_t *data, uint16_t length);
+    int (*connection_lossy_data_callback)(void *object, int id, const uint8_t *data, uint16_t length);
     void *connection_lossy_data_callback_object;
     int connection_lossy_data_callback_id;
 
@@ -157,6 +157,8 @@ typedef struct {
     Node_format tcp_relays[MAX_TCP_RELAYS_PEER];
     uint16_t num_tcp_relays;
 
+    uint8_t maximum_speed_reached;
+
     pthread_mutex_t mutex;
 } Crypto_Connection;
 
@@ -218,14 +220,14 @@ int accept_crypto_connection(Net_Crypto *c, New_Connection *n_c);
  * return -1 on failure.
  * return connection id on success.
  */
-int new_crypto_connection(Net_Crypto *c, uint8_t *real_public_key);
+int new_crypto_connection(Net_Crypto *c, const uint8_t *real_public_key);
 
 /* Copy friends DHT public key into dht_key.
  *
  * return 0 on failure (no key copied).
  * return timestamp on success (key copied).
  */
-uint64_t get_connection_dht_key(Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key);
+uint64_t get_connection_dht_key(const Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key);
 
 /* Set the DHT public key of the crypto connection.
  * timestamp is the time (current_time_monotonic()) at which the key was last confirmed belonging to
@@ -234,7 +236,8 @@ uint64_t get_connection_dht_key(Net_Crypto *c, int crypt_connection_id, uint8_t
  * return -1 on failure.
  * return 0 on success.
  */
-int set_connection_dht_public_key(Net_Crypto *c, int crypt_connection_id, uint8_t *dht_public_key, uint64_t timestamp);
+int set_connection_dht_public_key(const Net_Crypto *c, int crypt_connection_id, const uint8_t *dht_public_key,
+                                  uint64_t timestamp);
 
 /* Set the direct ip of the crypto connection.
  *
@@ -253,8 +256,8 @@ int set_direct_ip_port(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port);
  * return -1 on failure.
  * return 0 on success.
  */
-int connection_status_handler(Net_Crypto *c, int crypt_connection_id, int (*connection_status_callback)(void *object,
-                              int id, uint8_t status), void *object, int id);
+int connection_status_handler(const Net_Crypto *c, int crypt_connection_id,
+                              int (*connection_status_callback)(void *object, int id, uint8_t status), void *object, int id);
 
 /* Set function to be called when connection with crypt_connection_id receives a lossless data packet of length.
  *
@@ -264,7 +267,7 @@ int connection_status_handler(Net_Crypto *c, int crypt_connection_id, int (*conn
  * return -1 on failure.
  * return 0 on success.
  */
-int connection_data_handler(Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
+int connection_data_handler(const Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
                             int id, uint8_t *data, uint16_t length), void *object, int id);
 
 
@@ -277,12 +280,13 @@ int connection_data_handler(Net_Crypto *c, int crypt_connection_id, int (*connec
  * return 0 on success.
  */
 int connection_lossy_data_handler(Net_Crypto *c, int crypt_connection_id,
-                                  int (*connection_lossy_data_callback)(void *object, int id, uint8_t *data, uint16_t length), void *object, int id);
+                                  int (*connection_lossy_data_callback)(void *object, int id, const uint8_t *data, uint16_t length), void *object,
+                                  int id);
 
 /* returns the number of packet slots left in the sendbuffer.
  * return 0 if failure.
  */
-uint32_t crypto_num_free_sendqueue_slots(Net_Crypto *c, int crypt_connection_id);
+uint32_t crypto_num_free_sendqueue_slots(const Net_Crypto *c, int crypt_connection_id);
 
 /* Sends a lossless cryptopacket.
  *
@@ -291,28 +295,28 @@ uint32_t crypto_num_free_sendqueue_slots(Net_Crypto *c, int crypt_connection_id)
  *
  * The first byte of data must be in the CRYPTO_RESERVED_PACKETS to PACKET_ID_LOSSY_RANGE_START range.
  */
-int64_t write_cryptpacket(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint32_t length);
+int64_t write_cryptpacket(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length);
 
 /* return -1 on failure.
  * return 0 on success.
  *
  * Sends a lossy cryptopacket. (first byte must in the PACKET_ID_LOSSY_RANGE_*)
  */
-int send_lossy_cryptpacket(Net_Crypto *c, int crypt_connection_id, uint8_t *data, uint32_t length);
+int send_lossy_cryptpacket(const Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length);
 
 /* Add a tcp relay, associating it to a crypt_connection_id.
  *
  * return 0 if it was added.
  * return -1 if it wasn't.
  */
-int add_tcp_relay_peer(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port, uint8_t *public_key);
+int add_tcp_relay_peer(Net_Crypto *c, int crypt_connection_id, IP_Port ip_port, const uint8_t *public_key);
 
 /* Add a tcp relay to the array.
  *
  * return 0 if it was added.
  * return -1 if it wasn't.
  */
-int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, uint8_t *public_key);
+int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, const uint8_t *public_key);
 
 /* Copy a maximum of num TCP relays we are connected to to tcp_relays.
  * NOTE that the family of the copied ip ports will be set to TCP_INET or TCP_INET6.
@@ -320,7 +324,7 @@ int add_tcp_relay(Net_Crypto *c, IP_Port ip_port, uint8_t *public_key);
  * return number of relays copied to tcp_relays on success.
  * return 0 on failure.
  */
-unsigned int copy_connected_tcp_relays(Net_Crypto *c, Node_format *tcp_relays, uint16_t num);
+unsigned int copy_connected_tcp_relays(const Net_Crypto *c, Node_format *tcp_relays, uint16_t num);
 
 /* Kill a crypto connection.
  *
@@ -334,7 +338,7 @@ int crypto_kill(Net_Crypto *c, int crypt_connection_id);
  *
  * sets direct_connected to 1 if connection connects directly to other, 0 if it isn't.
  */
-unsigned int crypto_connection_status(Net_Crypto *c, int crypt_connection_id, uint8_t *direct_connected);
+unsigned int crypto_connection_status(const Net_Crypto *c, int crypt_connection_id, uint8_t *direct_connected);
 
 
 /* Generate our public and private keys.
@@ -345,7 +349,7 @@ void new_keys(Net_Crypto *c);
 /* Save the public and private keys to the keys array.
  *  Length must be crypto_box_PUBLICKEYBYTES + crypto_box_SECRETKEYBYTES.
  */
-void save_keys(Net_Crypto *c, uint8_t *keys);
+void save_keys(const Net_Crypto *c, uint8_t *keys);
 
 /* Load the public and private keys from the keys array.
  *  Length must be crypto_box_PUBLICKEYBYTES + crypto_box_SECRETKEYBYTES.
@@ -359,7 +363,7 @@ Net_Crypto *new_net_crypto(DHT *dht);
 
 /* return the optimal interval in ms for running do_net_crypto.
  */
-uint32_t crypto_run_interval(Net_Crypto *c);
+uint32_t crypto_run_interval(const Net_Crypto *c);
 
 /* Main loop. */
 void do_net_crypto(Net_Crypto *c);
diff --git a/toxcore/network.c b/toxcore/network.c
index 05b2ce2e..0009a558 100644
--- a/toxcore/network.c
+++ b/toxcore/network.c
@@ -181,13 +181,13 @@ int set_socket_dualstack(sock_t sock)
 {
     int ipv6only = 0;
     socklen_t optsize = sizeof(ipv6only);
-    int res = getsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void*)&ipv6only, &optsize);
+    int res = getsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void *)&ipv6only, &optsize);
 
     if ((res == 0) && (ipv6only == 0))
         return 1;
 
     ipv6only = 0;
-    return (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void*)&ipv6only, sizeof(ipv6only)) == 0);
+    return (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void *)&ipv6only, sizeof(ipv6only)) == 0);
 }
 
 
diff --git a/toxcore/onion.c b/toxcore/onion.c
index ac654689..1915324f 100644
--- a/toxcore/onion.c
+++ b/toxcore/onion.c
@@ -54,7 +54,7 @@ static void change_symmetric_key(Onion *onion)
  * return -1 on failure.
  * return 0 on success.
  */
-int create_onion_path(DHT *dht, Onion_Path *new_path, Node_format *nodes)
+int create_onion_path(const DHT *dht, Onion_Path *new_path, const Node_format *nodes)
 {
     if (!new_path || !nodes)
         return -1;
@@ -93,8 +93,8 @@ int create_onion_path(DHT *dht, Onion_Path *new_path, Node_format *nodes)
  * return -1 on failure.
  * return length of created packet on success.
  */
-int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, IP_Port dest, uint8_t *data,
-                        uint32_t length)
+int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, IP_Port dest,
+                        const uint8_t *data, uint32_t length)
 {
     if (1 + length + SEND_1 > max_packet_length || length == 0)
         return -1;
@@ -149,7 +149,7 @@ int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, Onion_Path
  * return -1 on failure.
  * return 0 on success.
  */
-int send_onion_packet(Networking_Core *net, Onion_Path *path, IP_Port dest, uint8_t *data, uint32_t length)
+int send_onion_packet(Networking_Core *net, const Onion_Path *path, IP_Port dest, const uint8_t *data, uint32_t length)
 {
     uint8_t packet[ONION_MAX_PACKET_SIZE];
     int len = create_onion_packet(packet, sizeof(packet), path, dest, data, length);
@@ -209,7 +209,7 @@ static int handle_send_initial(void *object, IP_Port source, const uint8_t *pack
     return onion_send_1(onion, plain, len, source, packet + 1);
 }
 
-int onion_send_1(Onion *onion, uint8_t *plain, uint32_t len, IP_Port source, const uint8_t *nonce)
+int onion_send_1(const Onion *onion, const uint8_t *plain, uint32_t len, IP_Port source, const uint8_t *nonce)
 {
     IP_Port send_to;
     ipport_unpack(&send_to, plain);
diff --git a/toxcore/onion.h b/toxcore/onion.h
index cd12fe2b..527f5c60 100644
--- a/toxcore/onion.h
+++ b/toxcore/onion.h
@@ -76,7 +76,7 @@ typedef struct {
  * return -1 on failure.
  * return 0 on success.
  */
-int create_onion_path(DHT *dht, Onion_Path *new_path, Node_format *nodes);
+int create_onion_path(const DHT *dht, Onion_Path *new_path, const Node_format *nodes);
 
 /* Create a onion packet.
  *
@@ -87,8 +87,8 @@ int create_onion_path(DHT *dht, Onion_Path *new_path, Node_format *nodes);
  * return -1 on failure.
  * return length of created packet on success.
  */
-int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, IP_Port dest, uint8_t *data,
-                        uint32_t length);
+int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, IP_Port dest,
+                        const uint8_t *data, uint32_t length);
 
 /* Create and send a onion packet.
  *
@@ -98,7 +98,7 @@ int create_onion_packet(uint8_t *packet, uint16_t max_packet_length, Onion_Path
  * return -1 on failure.
  * return 0 on success.
  */
-int send_onion_packet(Networking_Core *net, Onion_Path *path, IP_Port dest, uint8_t *data, uint32_t length);
+int send_onion_packet(Networking_Core *net, const Onion_Path *path, IP_Port dest, const uint8_t *data, uint32_t length);
 
 /* Create and send a onion response sent initially to dest with.
  * Maximum length of data is ONION_RESPONSE_MAX_DATA_SIZE.
@@ -118,7 +118,7 @@ int send_onion_response(Networking_Core *net, IP_Port dest, const uint8_t *data,
  * Source family must be set to something else than AF_INET6 or AF_INET so that the callback gets called
  * when the response is received.
  */
-int onion_send_1(Onion *onion, uint8_t *plain, uint32_t len, IP_Port source, const uint8_t *nonce);
+int onion_send_1(const Onion *onion, const uint8_t *plain, uint32_t len, IP_Port source, const uint8_t *nonce);
 
 /* Set the callback to be called when the dest ip_port doesn't have AF_INET6 or AF_INET as the family.
  *
diff --git a/toxcore/onion_announce.c b/toxcore/onion_announce.c
index 658d4c11..dff05135 100644
--- a/toxcore/onion_announce.c
+++ b/toxcore/onion_announce.c
@@ -49,9 +49,9 @@
  * return -1 on failure.
  * return packet length on success.
  */
-int create_announce_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, Node_format dest,
-                            uint8_t *public_key, uint8_t *secret_key, uint8_t *ping_id, uint8_t *client_id, uint8_t *data_public_key,
-                            uint64_t sendback_data)
+int create_announce_request(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, Node_format dest,
+                            const uint8_t *public_key, const uint8_t *secret_key, const uint8_t *ping_id, const uint8_t *client_id,
+                            const uint8_t *data_public_key, uint64_t sendback_data)
 {
     uint8_t plain[ONION_PING_ID_SIZE + crypto_box_PUBLICKEYBYTES + crypto_box_PUBLICKEYBYTES +
                   ONION_ANNOUNCE_SENDBACK_DATA_LENGTH];
@@ -89,8 +89,9 @@ int create_announce_request(uint8_t *packet, uint16_t max_packet_length, Onion_P
  * return -1 on failure.
  * return 0 on success.
  */
-int create_data_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, IP_Port dest,
-                        uint8_t *public_key, uint8_t *encrypt_public_key, uint8_t *nonce, uint8_t *data, uint16_t length)
+int create_data_request(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, IP_Port dest,
+                        const uint8_t *public_key, const uint8_t *encrypt_public_key, const uint8_t *nonce, const uint8_t *data,
+                        uint16_t length)
 {
     if ((unsigned int)DATA_REQUEST_MIN_SIZE + length > ONION_MAX_DATA_SIZE)
         return -1;
@@ -129,8 +130,9 @@ int create_data_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path
  * return -1 on failure.
  * return 0 on success.
  */
-int send_announce_request(Networking_Core *net, Onion_Path *path, Node_format dest, uint8_t *public_key,
-                          uint8_t *secret_key, uint8_t *ping_id, uint8_t *client_id, uint8_t *data_public_key, uint64_t sendback_data)
+int send_announce_request(Networking_Core *net, const Onion_Path *path, Node_format dest, const uint8_t *public_key,
+                          const uint8_t *secret_key, const uint8_t *ping_id, const uint8_t *client_id, const uint8_t *data_public_key,
+                          uint64_t sendback_data)
 {
     uint8_t packet[ONION_MAX_PACKET_SIZE];
     int len = create_announce_request(packet, sizeof(packet), path, dest, public_key, secret_key, ping_id, client_id,
@@ -159,8 +161,8 @@ int send_announce_request(Networking_Core *net, Onion_Path *path, Node_format de
  * return -1 on failure.
  * return 0 on success.
  */
-int send_data_request(Networking_Core *net, Onion_Path *path, IP_Port dest, uint8_t *public_key,
-                      uint8_t *encrypt_public_key, uint8_t *nonce, uint8_t *data, uint16_t length)
+int send_data_request(Networking_Core *net, const Onion_Path *path, IP_Port dest, const uint8_t *public_key,
+                      const uint8_t *encrypt_public_key, const uint8_t *nonce, const uint8_t *data, uint16_t length)
 {
     uint8_t packet[ONION_MAX_PACKET_SIZE];
     int len = create_data_request(packet, sizeof(packet), path, dest, public_key, encrypt_public_key, nonce, data, length);
@@ -175,8 +177,8 @@ int send_data_request(Networking_Core *net, Onion_Path *path, IP_Port dest, uint
 }
 
 /* Generate a ping_id and put it in ping_id */
-static void generate_ping_id(Onion_Announce *onion_a, uint64_t time, const uint8_t *public_key, IP_Port ret_ip_port,
-                             uint8_t *ping_id)
+static void generate_ping_id(const Onion_Announce *onion_a, uint64_t time, const uint8_t *public_key,
+                             IP_Port ret_ip_port, uint8_t *ping_id)
 {
     time /= PING_ID_TIMEOUT;
     uint8_t data[crypto_box_KEYBYTES + sizeof(time) + crypto_box_PUBLICKEYBYTES + sizeof(ret_ip_port)];
diff --git a/toxcore/onion_announce.h b/toxcore/onion_announce.h
index 42f63ccd..d31355e5 100644
--- a/toxcore/onion_announce.h
+++ b/toxcore/onion_announce.h
@@ -75,9 +75,9 @@ typedef struct {
  * return -1 on failure.
  * return packet length on success.
  */
-int create_announce_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, Node_format dest,
-                            uint8_t *public_key, uint8_t *secret_key, uint8_t *ping_id, uint8_t *client_id, uint8_t *data_public_key,
-                            uint64_t sendback_data);
+int create_announce_request(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, Node_format dest,
+                            const uint8_t *public_key, const uint8_t *secret_key, const uint8_t *ping_id, const uint8_t *client_id,
+                            const uint8_t *data_public_key, uint64_t sendback_data);
 
 /* Create an onion data request packet in packet of max_packet_length (recommended size ONION_MAX_PACKET_SIZE).
  *
@@ -93,8 +93,9 @@ int create_announce_request(uint8_t *packet, uint16_t max_packet_length, Onion_P
  * return -1 on failure.
  * return 0 on success.
  */
-int create_data_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path *path, IP_Port dest,
-                        uint8_t *public_key, uint8_t *encrypt_public_key, uint8_t *nonce, uint8_t *data, uint16_t length);
+int create_data_request(uint8_t *packet, uint16_t max_packet_length, const Onion_Path *path, IP_Port dest,
+                        const uint8_t *public_key, const uint8_t *encrypt_public_key, const uint8_t *nonce, const uint8_t *data,
+                        uint16_t length);
 
 /* Create and send an onion announce request packet.
  *
@@ -110,8 +111,9 @@ int create_data_request(uint8_t *packet, uint16_t max_packet_length, Onion_Path
  * return -1 on failure.
  * return 0 on success.
  */
-int send_announce_request(Networking_Core *net, Onion_Path *path, Node_format dest, uint8_t *public_key,
-                          uint8_t *secret_key, uint8_t *ping_id, uint8_t *client_id, uint8_t *data_public_key, uint64_t sendback_data);
+int send_announce_request(Networking_Core *net, const Onion_Path *path, Node_format dest, const uint8_t *public_key,
+                          const uint8_t *secret_key, const uint8_t *ping_id, const uint8_t *client_id, const uint8_t *data_public_key,
+                          uint64_t sendback_data);
 
 /* Create and send an onion data request packet.
  *
@@ -129,8 +131,8 @@ int send_announce_request(Networking_Core *net, Onion_Path *path, Node_format de
  * return -1 on failure.
  * return 0 on success.
  */
-int send_data_request(Networking_Core *net, Onion_Path *path, IP_Port dest, uint8_t *public_key,
-                      uint8_t *encrypt_public_key, uint8_t *nonce, uint8_t *data, uint16_t length);
+int send_data_request(Networking_Core *net, const Onion_Path *path, IP_Port dest, const uint8_t *public_key,
+                      const uint8_t *encrypt_public_key, const uint8_t *nonce, const uint8_t *data, uint16_t length);
 
 
 Onion_Announce *new_onion_announce(DHT *dht);
diff --git a/toxcore/onion_client.c b/toxcore/onion_client.c
index 40701e2d..7d0efc79 100644
--- a/toxcore/onion_client.c
+++ b/toxcore/onion_client.c
@@ -38,7 +38,7 @@
  * return -1 if nodes are suitable for creating a new path.
  * return path number of already existing similar path if one already exists.
  */
-static int is_path_used(Onion_Client_Paths *onion_paths, Node_format *nodes)
+static int is_path_used(const Onion_Client_Paths *onion_paths, const Node_format *nodes)
 {
     uint32_t i;
 
@@ -68,7 +68,7 @@ static int is_path_used(Onion_Client_Paths *onion_paths, Node_format *nodes)
  * TODO: Make this function better, it currently probably is vulnerable to some attacks that
  * could de anonimize us.
  */
-static int random_path(DHT *dht, Onion_Client_Paths *onion_paths, uint32_t pathnum, Onion_Path *path)
+static int random_path(const DHT *dht, Onion_Client_Paths *onion_paths, uint32_t pathnum, Onion_Path *path)
 {
     if (pathnum >= NUMBER_ONION_PATHS)
         pathnum = rand() % NUMBER_ONION_PATHS;
@@ -130,7 +130,7 @@ static uint32_t set_path_timeouts(Onion_Client *onion_c, uint32_t num, IP_Port s
  * return -1 on failure.
  * return 0 on success.
  */
-static int send_onion_packet_tcp_udp(const Onion_Client *onion_c, IP_Port ip_port, uint8_t *data, uint32_t length)
+static int send_onion_packet_tcp_udp(const Onion_Client *onion_c, IP_Port ip_port, const uint8_t *data, uint32_t length)
 {
     if (ip_port.ip.family == AF_INET || ip_port.ip.family == AF_INET6) {
         if ((uint32_t)sendpacket(onion_c->net, ip_port, data, length) != length)
@@ -157,7 +157,8 @@ static int send_onion_packet_tcp_udp(const Onion_Client *onion_c, IP_Port ip_por
  * return 0 on success
  *
  */
-static int new_sendback(Onion_Client *onion_c, uint32_t num, uint8_t *public_key, IP_Port ip_port, uint64_t *sendback)
+static int new_sendback(Onion_Client *onion_c, uint32_t num, const uint8_t *public_key, IP_Port ip_port,
+                        uint64_t *sendback)
 {
     uint8_t data[sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES + sizeof(IP_Port)];
     memcpy(data, &num, sizeof(uint32_t));
@@ -198,8 +199,8 @@ static uint32_t check_sendback(Onion_Client *onion_c, const uint8_t *sendback, u
     return num;
 }
 
-static int client_send_announce_request(Onion_Client *onion_c, uint32_t num, IP_Port dest, uint8_t *dest_pubkey,
-                                        uint8_t *ping_id, uint32_t pathnum)
+static int client_send_announce_request(Onion_Client *onion_c, uint32_t num, IP_Port dest, const uint8_t *dest_pubkey,
+                                        const uint8_t *ping_id, uint32_t pathnum)
 {
     if (num > onion_c->num_friends)
         return -1;
@@ -279,8 +280,8 @@ static int cmp_entry(const void *a, const void *b)
     return 0;
 }
 
-static int client_add_to_list(Onion_Client *onion_c, uint32_t num, uint8_t *public_key, IP_Port ip_port,
-                              uint8_t is_stored, uint8_t *pingid_or_key, IP_Port source)
+static int client_add_to_list(Onion_Client *onion_c, uint32_t num, const uint8_t *public_key, IP_Port ip_port,
+                              uint8_t is_stored, const uint8_t *pingid_or_key, IP_Port source)
 {
     if (num > onion_c->num_friends)
         return -1;
@@ -338,7 +339,7 @@ static int client_add_to_list(Onion_Client *onion_c, uint32_t num, uint8_t *publ
     return 0;
 }
 
-static int good_to_ping(Last_Pinged *last_pinged, uint8_t *last_pinged_index, uint8_t *client_id)
+static int good_to_ping(Last_Pinged *last_pinged, uint8_t *last_pinged_index, const uint8_t *client_id)
 {
     uint32_t i;
 
@@ -354,7 +355,7 @@ static int good_to_ping(Last_Pinged *last_pinged, uint8_t *last_pinged_index, ui
     return 1;
 }
 
-static int client_ping_nodes(Onion_Client *onion_c, uint32_t num, Node_format *nodes, uint16_t num_nodes,
+static int client_ping_nodes(Onion_Client *onion_c, uint32_t num, const Node_format *nodes, uint16_t num_nodes,
                              IP_Port source)
 {
     if (num > onion_c->num_friends)
@@ -630,7 +631,7 @@ int send_onion_data(const Onion_Client *onion_c, int friend_num, const uint8_t *
  * return the number of packets sent on success
  * return -1 on failure.
  */
-static int send_dht_fakeid(Onion_Client *onion_c, int friend_num, uint8_t *data, uint32_t length)
+static int send_dht_fakeid(const Onion_Client *onion_c, int friend_num, const uint8_t *data, uint32_t length)
 {
     if ((uint32_t)friend_num >= onion_c->num_friends)
         return -1;
@@ -693,7 +694,7 @@ static int handle_dht_fakeid(void *object, IP_Port source, const uint8_t *source
  * return the number of packets sent on success
  * return -1 on failure.
  */
-static int send_fakeid_announce(Onion_Client *onion_c, uint16_t friend_num, uint8_t onion_dht_both)
+static int send_fakeid_announce(const Onion_Client *onion_c, uint16_t friend_num, uint8_t onion_dht_both)
 {
     if (friend_num >= onion_c->num_friends)
         return -1;
@@ -851,7 +852,7 @@ int onion_delfriend(Onion_Client *onion_c, int friend_num)
  * return 0 on success.
  */
 int recv_tcp_relay_handler(Onion_Client *onion_c, int friend_num, int (*tcp_relay_node_callback)(void *object,
-                           uint32_t number, IP_Port ip_port, uint8_t *public_key), void *object, uint32_t number)
+                           uint32_t number, IP_Port ip_port, const uint8_t *public_key), void *object, uint32_t number)
 {
     if ((uint32_t)friend_num >= onion_c->num_friends)
         return -1;
@@ -905,7 +906,7 @@ int onion_set_friend_DHT_pubkey(Onion_Client *onion_c, int friend_num, const uin
  * return 0 on failure (no key copied).
  * return timestamp on success (key copied).
  */
-uint64_t onion_getfriend_DHT_pubkey(Onion_Client *onion_c, int friend_num, uint8_t *dht_key)
+uint64_t onion_getfriend_DHT_pubkey(const Onion_Client *onion_c, int friend_num, uint8_t *dht_key)
 {
     if ((uint32_t)friend_num >= onion_c->num_friends)
         return 0;
@@ -927,7 +928,7 @@ uint64_t onion_getfriend_DHT_pubkey(Onion_Client *onion_c, int friend_num, uint8
  *  return  1, ip if client_id refers to a friend and we found him
  *
  */
-int onion_getfriendip(Onion_Client *onion_c, int friend_num, IP_Port *ip_port)
+int onion_getfriendip(const Onion_Client *onion_c, int friend_num, IP_Port *ip_port)
 {
     uint8_t dht_public_key[crypto_box_PUBLICKEYBYTES];
 
diff --git a/toxcore/onion_client.h b/toxcore/onion_client.h
index a74783f6..bf891e7a 100644
--- a/toxcore/onion_client.h
+++ b/toxcore/onion_client.h
@@ -97,7 +97,7 @@ typedef struct {
     Last_Pinged last_pinged[MAX_STORED_PINGED_NODES];
     uint8_t last_pinged_index;
 
-    int (*tcp_relay_node_callback)(void *object, uint32_t number, IP_Port ip_port, uint8_t *public_key);
+    int (*tcp_relay_node_callback)(void *object, uint32_t number, IP_Port ip_port, const uint8_t *public_key);
     void *tcp_relay_node_callback_object;
     uint32_t tcp_relay_node_callback_number;
 } Onion_Friend;
@@ -171,7 +171,7 @@ int onion_set_friend_online(Onion_Client *onion_c, int friend_num, uint8_t is_on
  *  return  1, ip if client_id refers to a friend and we found him
  *
  */
-int onion_getfriendip(Onion_Client *onion_c, int friend_num, IP_Port *ip_port);
+int onion_getfriendip(const Onion_Client *onion_c, int friend_num, IP_Port *ip_port);
 
 /* Set the function for this friend that will be callbacked with object and number
  * when that friends gives us one of the TCP relays he is connected to.
@@ -182,7 +182,7 @@ int onion_getfriendip(Onion_Client *onion_c, int friend_num, IP_Port *ip_port);
  * return 0 on success.
  */
 int recv_tcp_relay_handler(Onion_Client *onion_c, int friend_num, int (*tcp_relay_node_callback)(void *object,
-                           uint32_t number, IP_Port ip_port, uint8_t *public_key), void *object, uint32_t number);
+                           uint32_t number, IP_Port ip_port, const uint8_t *public_key), void *object, uint32_t number);
 
 /* Set a friends DHT public key.
  * timestamp is the time (current_time_monotonic()) at which the key was last confirmed belonging to
@@ -198,7 +198,7 @@ int onion_set_friend_DHT_pubkey(Onion_Client *onion_c, int friend_num, const uin
  * return 0 on failure (no key copied).
  * return timestamp on success (key copied).
  */
-uint64_t onion_getfriend_DHT_pubkey(Onion_Client *onion_c, int friend_num, uint8_t *dht_key);
+uint64_t onion_getfriend_DHT_pubkey(const Onion_Client *onion_c, int friend_num, uint8_t *dht_key);
 
 #define ONION_DATA_IN_RESPONSE_MIN_SIZE (crypto_box_PUBLICKEYBYTES + crypto_box_MACBYTES)
 #define ONION_CLIENT_MAX_DATA_SIZE (MAX_DATA_REQUEST_SIZE - ONION_DATA_IN_RESPONSE_MIN_SIZE)
diff --git a/toxcore/tox.c b/toxcore/tox.c
index 79e4c042..1b6597ba 100644
--- a/toxcore/tox.c
+++ b/toxcore/tox.c
@@ -38,9 +38,9 @@ typedef struct Messenger Tox;
  * Format: [client_id (32 bytes)][nospam number (4 bytes)][checksum (2 bytes)]
  *
  */
-void tox_get_address(Tox *tox, uint8_t *address)
+void tox_get_address(const Tox *tox, uint8_t *address)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     getaddress(m, address);
 }
 
@@ -61,7 +61,7 @@ void tox_get_address(Tox *tox, uint8_t *address)
  *  (the nospam for that friend was set to the new one).
  *  return FAERR_NOMEM if increasing the friend list size fails.
  */
-int32_t tox_add_friend(Tox *tox, uint8_t *address, uint8_t *data, uint16_t length)
+int32_t tox_add_friend(Tox *tox, const uint8_t *address, const uint8_t *data, uint16_t length)
 {
     Messenger *m = tox;
     return m_addfriend(m, address, data, length);
@@ -81,9 +81,9 @@ int32_t tox_add_friend_norequest(Tox *tox, const uint8_t *client_id)
 /*  return the friend number associated to that client id.
  *  return -1 if no such friend.
  */
-int32_t tox_get_friend_number(Tox *tox, uint8_t *client_id)
+int32_t tox_get_friend_number(const Tox *tox, const uint8_t *client_id)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return getfriend_id(m, client_id);
 }
 
@@ -93,9 +93,9 @@ int32_t tox_get_friend_number(Tox *tox, uint8_t *client_id)
  *  return 0 if success.
  *  return -1 if failure.
  */
-int tox_get_client_id(Tox *tox, int32_t friendnumber, uint8_t *client_id)
+int tox_get_client_id(const Tox *tox, int32_t friendnumber, uint8_t *client_id)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return getclient_id(m, friendnumber, client_id);
 }
 
@@ -112,9 +112,9 @@ int tox_del_friend(Tox *tox, int32_t friendnumber)
  *  return 0 if friend is not connected to us (Offline).
  *  return -1 on failure.
  */
-int tox_get_friend_connection_status(Tox *tox, int32_t friendnumber)
+int tox_get_friend_connection_status(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_friend_connectionstatus(m, friendnumber);
 }
 
@@ -123,9 +123,9 @@ int tox_get_friend_connection_status(Tox *tox, int32_t friendnumber)
  *  return 1 if friend exists.
  *  return 0 if friend doesn't exist.
  */
-int tox_friend_exists(Tox *tox, int32_t friendnumber)
+int tox_friend_exists(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_friend_exists(m, friendnumber);
 }
 
@@ -144,7 +144,8 @@ uint32_t tox_send_message(Tox *tox, int32_t friendnumber, const uint8_t *message
     return m_sendmessage(m, friendnumber, message, length);
 }
 
-uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid, uint8_t *message, uint32_t length)
+uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid, const uint8_t *message,
+                                 uint32_t length)
 {
     Messenger *m = tox;
     return m_sendmessage_withid(m, friendnumber, theid, message, length);
@@ -160,13 +161,13 @@ uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid,
  *  m_sendaction_withid will send an action message with the id of your choosing,
  *  however we can generate an id for you by calling plain m_sendaction.
  */
-uint32_t tox_send_action(Tox *tox, int32_t friendnumber, uint8_t *action, uint32_t length)
+uint32_t tox_send_action(Tox *tox, int32_t friendnumber, const uint8_t *action, uint32_t length)
 {
     Messenger *m = tox;
     return m_sendaction(m, friendnumber, action, length);
 }
 
-uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid, uint8_t *action, uint32_t length)
+uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid, const uint8_t *action, uint32_t length)
 {
     Messenger *m = tox;
     return m_sendaction_withid(m, friendnumber, theid, action, length);
@@ -180,7 +181,7 @@ uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid,
  *  return 0 if success.
  *  return -1 if failure.
  */
-int tox_set_name(Tox *tox, uint8_t *name, uint16_t length)
+int tox_set_name(Tox *tox, const uint8_t *name, uint16_t length)
 {
     Messenger *m = tox;
     return setname(m, name, length);
@@ -193,9 +194,9 @@ int tox_set_name(Tox *tox, uint8_t *name, uint16_t length)
  *  return length of the name.
  *  return 0 on error.
  */
-uint16_t tox_get_self_name(Tox *tox, uint8_t *name)
+uint16_t tox_get_self_name(const Tox *tox, uint8_t *name)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return getself_name(m, name);
 }
 
@@ -205,24 +206,24 @@ uint16_t tox_get_self_name(Tox *tox, uint8_t *name)
  *  return length of name (with the NULL terminator) if success.
  *  return -1 if failure.
  */
-int tox_get_name(Tox *tox, int32_t friendnumber, uint8_t *name)
+int tox_get_name(const Tox *tox, int32_t friendnumber, uint8_t *name)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return getname(m, friendnumber, name);
 }
 
 /*  returns the length of name on success.
  *  returns -1 on failure.
  */
-int tox_get_name_size(Tox *tox, int32_t friendnumber)
+int tox_get_name_size(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_name_size(m, friendnumber);
 }
 
-int tox_get_self_name_size(Tox *tox)
+int tox_get_self_name_size(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_self_name_size(m);
 }
 
@@ -231,7 +232,7 @@ int tox_get_self_name_size(Tox *tox)
  *
  *  return 0 on success, -1 on failure.
  */
-int tox_set_status_message(Tox *tox, uint8_t *status, uint16_t length)
+int tox_set_status_message(Tox *tox, const uint8_t *status, uint16_t length)
 {
     Messenger *m = tox;
     return m_set_statusmessage(m, status, length);
@@ -246,15 +247,15 @@ int tox_set_user_status(Tox *tox, uint8_t status)
 /*  returns the length of status message on success.
  *  returns -1 on failure.
  */
-int tox_get_status_message_size(Tox *tox, int32_t friendnumber)
+int tox_get_status_message_size(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_statusmessage_size(m, friendnumber);
 }
 
-int tox_get_self_status_message_size(Tox *tox)
+int tox_get_self_status_message_size(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_self_statusmessage_size(m);
 }
 
@@ -262,15 +263,15 @@ int tox_get_self_status_message_size(Tox *tox)
  * Get the size you need to allocate from m_get_statusmessage_size.
  * The self variant will copy our own status message.
  */
-int tox_get_status_message(Tox *tox, int32_t friendnumber, uint8_t *buf, uint32_t maxlen)
+int tox_get_status_message(const Tox *tox, int32_t friendnumber, uint8_t *buf, uint32_t maxlen)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_copy_statusmessage(m, friendnumber, buf, maxlen);
 }
 
-int tox_get_self_status_message(Tox *tox, uint8_t *buf, uint32_t maxlen)
+int tox_get_self_status_message(const Tox *tox, uint8_t *buf, uint32_t maxlen)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_copy_self_statusmessage(m, buf, maxlen);
 }
 
@@ -279,24 +280,24 @@ int tox_get_self_status_message(Tox *tox, uint8_t *buf, uint32_t maxlen)
  * As above, the self variant will return our own USERSTATUS.
  * If friendnumber is invalid, this shall return USERSTATUS_INVALID.
  */
-uint8_t tox_get_user_status(Tox *tox, int32_t friendnumber)
+uint8_t tox_get_user_status(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_userstatus(m, friendnumber);
 }
 
-uint8_t tox_get_self_user_status(Tox *tox)
+uint8_t tox_get_self_user_status(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_self_userstatus(m);
 }
 
 /* returns timestamp of last time friendnumber was seen online, or 0 if never seen.
  * returns -1 on error.
  */
-uint64_t tox_get_last_online(Tox *tox, int32_t friendnumber)
+uint64_t tox_get_last_online(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_last_online(m, friendnumber);
 }
 
@@ -317,9 +318,9 @@ int tox_set_user_is_typing(Tox *tox, int32_t friendnumber, uint8_t is_typing)
  * returns 0 if friend is not typing.
  * returns 1 if friend is typing.
  */
-uint8_t tox_get_is_typing(Tox *tox, int32_t friendnumber)
+uint8_t tox_get_is_typing(const Tox *tox, int32_t friendnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_get_istyping(m, friendnumber);
 }
 
@@ -335,16 +336,16 @@ void tox_set_sends_receipts(Tox *tox, int32_t friendnumber, int yesno)
 /* Return the number of friends in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_friendlist. */
-uint32_t tox_count_friendlist(Tox *tox)
+uint32_t tox_count_friendlist(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return count_friendlist(m);
 }
 
 /* Return the number of online friends in the instance m. */
-uint32_t tox_get_num_online_friends(Tox *tox)
+uint32_t tox_get_num_online_friends(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return get_num_online_friends(m);
 }
 
@@ -353,9 +354,9 @@ uint32_t tox_get_num_online_friends(Tox *tox)
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t tox_get_friendlist(Tox *tox, int32_t *out_list, uint32_t list_size)
+uint32_t tox_get_friendlist(const Tox *tox, int32_t *out_list, uint32_t list_size)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return copy_friendlist(m, out_list, list_size);
 }
 
@@ -373,7 +374,7 @@ void tox_callback_friend_request(Tox *tox, void (*function)(Tox *tox, const uint
 /* Set the function that will be executed when a message from a friend is received.
  *  Function format is: function(int32_t friendnumber, uint8_t * message, uint32_t length)
  */
-void tox_callback_friend_message(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_friend_message(Tox *tox, void (*function)(Messenger *tox, int32_t, const uint8_t *, uint16_t, void *),
                                  void *userdata)
 {
     Messenger *m = tox;
@@ -383,7 +384,7 @@ void tox_callback_friend_message(Tox *tox, void (*function)(Messenger *tox, int3
 /* Set the function that will be executed when an action from a friend is received.
  *  function format is: function(int32_t friendnumber, uint8_t * action, uint32_t length)
  */
-void tox_callback_friend_action(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_friend_action(Tox *tox, void (*function)(Messenger *tox, int32_t, const uint8_t *, uint16_t, void *),
                                 void *userdata)
 {
     Messenger *m = tox;
@@ -394,7 +395,7 @@ void tox_callback_friend_action(Tox *tox, void (*function)(Messenger *tox, int32
  *  function(int32_t friendnumber, uint8_t *newname, uint16_t length)
  *  You are not responsible for freeing newname.
  */
-void tox_callback_name_change(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_name_change(Tox *tox, void (*function)(Messenger *tox, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata)
 {
     Messenger *m = tox;
@@ -405,7 +406,7 @@ void tox_callback_name_change(Tox *tox, void (*function)(Messenger *tox, int32_t
  *  function(int32_t friendnumber, uint8_t *newstatus, uint16_t length)
  *  You are not responsible for freeing newstatus.
  */
-void tox_callback_status_message(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_status_message(Tox *tox, void (*function)(Messenger *tox, int32_t, const uint8_t *, uint16_t, void *),
                                  void *userdata)
 {
     Messenger *m = tox;
@@ -468,9 +469,9 @@ void tox_callback_connection_status(Tox *tox, void (*function)(Messenger *tox, i
 
 /* Functions to get/set the nospam part of the id.
  */
-uint32_t tox_get_nospam(Tox *tox)
+uint32_t tox_get_nospam(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return get_nospam(&(m->fr));
 }
 
@@ -486,7 +487,8 @@ void tox_set_nospam(Tox *tox, uint32_t nospam)
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t *group_public_key, void *userdata)
  */
-void tox_callback_group_invite(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t *, void *), void *userdata)
+void tox_callback_group_invite(Tox *tox, void (*function)(Messenger *tox, int32_t, const uint8_t *, void *),
+                               void *userdata)
 {
     Messenger *m = tox;
     m_callback_group_invite(m, function, userdata);
@@ -496,7 +498,7 @@ void tox_callback_group_invite(Tox *tox, void (*function)(Messenger *tox, int32_
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void tox_callback_group_message(Tox *tox, void (*function)(Messenger *tox, int, int, uint8_t *, uint16_t, void *),
+void tox_callback_group_message(Tox *tox, void (*function)(Messenger *tox, int, int, const uint8_t *, uint16_t, void *),
                                 void *userdata)
 {
     Messenger *m = tox;
@@ -507,7 +509,7 @@ void tox_callback_group_message(Tox *tox, void (*function)(Messenger *tox, int,
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * action, uint16_t length, void *userdata)
  */
-void tox_callback_group_action(Tox *tox, void (*function)(Messenger *tox, int, int, uint8_t *, uint16_t, void *),
+void tox_callback_group_action(Tox *tox, void (*function)(Messenger *tox, int, int, const uint8_t *, uint16_t, void *),
                                void *userdata)
 {
     Messenger *m = tox;
@@ -552,9 +554,9 @@ int tox_del_groupchat(Tox *tox, int groupnumber)
  * return length of name if success
  * return -1 if failure
  */
-int tox_group_peername(Tox *tox, int groupnumber, int peernumber, uint8_t *name)
+int tox_group_peername(const Tox *tox, int groupnumber, int peernumber, uint8_t *name)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return m_group_peername(m, groupnumber, peernumber, name);
 }
 /* invite friendnumber to groupnumber
@@ -571,7 +573,7 @@ int tox_invite_friend(Tox *tox, int32_t friendnumber, int groupnumber)
  * returns group number on success
  * returns -1 on failure.
  */
-int tox_join_groupchat(Tox *tox, int32_t friendnumber, uint8_t *friend_group_public_key)
+int tox_join_groupchat(Tox *tox, int32_t friendnumber, const uint8_t *friend_group_public_key)
 {
     Messenger *m = tox;
     return join_groupchat(m, friendnumber, friend_group_public_key);
@@ -581,7 +583,7 @@ int tox_join_groupchat(Tox *tox, int32_t friendnumber, uint8_t *friend_group_pub
  * return 0 on success
  * return -1 on failure
  */
-int tox_group_message_send(Tox *tox, int groupnumber, uint8_t *message, uint32_t length)
+int tox_group_message_send(Tox *tox, int groupnumber, const uint8_t *message, uint32_t length)
 {
     Messenger *m = tox;
     return group_message_send(m, groupnumber, message, length);
@@ -591,7 +593,7 @@ int tox_group_message_send(Tox *tox, int groupnumber, uint8_t *message, uint32_t
  * return 0 on success
  * return -1 on failure
  */
-int tox_group_action_send(Tox *tox, int groupnumber, uint8_t *action, uint32_t length)
+int tox_group_action_send(Tox *tox, int groupnumber, const uint8_t *action, uint32_t length)
 {
     Messenger *m = tox;
     return group_action_send(m, groupnumber, action, length);
@@ -600,9 +602,9 @@ int tox_group_action_send(Tox *tox, int groupnumber, uint8_t *action, uint32_t l
 /* Return the number of peers in the group chat on success.
  * return -1 on failure
  */
-int tox_group_number_peers(Tox *tox, int groupnumber)
+int tox_group_number_peers(const Tox *tox, int groupnumber)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return group_number_peers(m, groupnumber);
 }
 
@@ -616,19 +618,19 @@ int tox_group_number_peers(Tox *tox, int groupnumber)
  *
  * return -1 on failure.
  */
-int tox_group_get_names(Tox *tox, int groupnumber, uint8_t names[][TOX_MAX_NAME_LENGTH], uint16_t lengths[],
+int tox_group_get_names(const Tox *tox, int groupnumber, uint8_t names[][TOX_MAX_NAME_LENGTH], uint16_t lengths[],
                         uint16_t length)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return group_names(m, groupnumber, names, lengths, length);
 }
 
 /* Return the number of chats in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_chatlist. */
-uint32_t tox_count_chatlist(Tox *tox)
+uint32_t tox_count_chatlist(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return count_chatlist(m);
 }
 
@@ -637,9 +639,9 @@ uint32_t tox_count_chatlist(Tox *tox)
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t tox_get_chatlist(Tox *tox, int *out_list, uint32_t list_size)
+uint32_t tox_get_chatlist(const Tox *tox, int *out_list, uint32_t list_size)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return copy_chatlist(m, out_list, list_size);
 }
 
@@ -651,9 +653,8 @@ uint32_t tox_get_chatlist(Tox *tox, int *out_list, uint32_t list_size)
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length, void *userdata)
  */
-void tox_callback_file_send_request(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, uint64_t, uint8_t *,
-                                    uint16_t,
-                                    void *), void *userdata)
+void tox_callback_file_send_request(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, uint64_t,
+                                    const uint8_t *, uint16_t, void *), void *userdata)
 {
     Messenger *m = tox;
     callback_file_sendrequest(m, function, userdata);
@@ -663,8 +664,8 @@ void tox_callback_file_send_request(Tox *tox, void (*function)(Messenger *tox, i
  *  Function(Tox *tox, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t control_type, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void tox_callback_file_control(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, uint8_t, uint8_t, uint8_t *,
-                               uint16_t, void *), void *userdata)
+void tox_callback_file_control(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, uint8_t, uint8_t,
+                               const uint8_t *, uint16_t, void *), void *userdata)
 {
     Messenger *m = tox;
     callback_file_control(m, function, userdata);
@@ -674,9 +675,8 @@ void tox_callback_file_control(Tox *tox, void (*function)(Messenger *tox, int32_
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void tox_callback_file_data(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, uint8_t *, uint16_t length,
-                            void *),
-                            void *userdata)
+void tox_callback_file_data(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, const uint8_t *,
+                            uint16_t length, void *), void *userdata)
 
 {
     Messenger *m = tox;
@@ -687,7 +687,8 @@ void tox_callback_file_data(Tox *tox, void (*function)(Messenger *tox, int32_t,
  *  return file number on success
  *  return -1 on failure
  */
-int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length)
+int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, const uint8_t *filename,
+                        uint16_t filename_length)
 {
     Messenger *m = tox;
     return new_filesender(m, friendnumber, filesize, filename, filename_length);
@@ -699,7 +700,7 @@ int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, uint8
  *  return -1 on failure
  */
 int tox_file_send_control(Tox *tox, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
-                          uint8_t *data, uint16_t length)
+                          const uint8_t *data, uint16_t length)
 {
     Messenger *m = tox;
     return file_control(m, friendnumber, send_receive, filenumber, message_id, data, length);
@@ -709,7 +710,7 @@ int tox_file_send_control(Tox *tox, int32_t friendnumber, uint8_t send_receive,
  *  return 0 on success
  *  return -1 on failure
  */
-int tox_file_send_data(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length)
+int tox_file_send_data(Tox *tox, int32_t friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length)
 {
     Messenger *m = tox;
     return file_data(m, friendnumber, filenumber, data, length);
@@ -720,7 +721,7 @@ int tox_file_send_data(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8
  *  return size on success
  *  return -1 on failure (currently will never return -1)
  */
-int tox_file_data_size(Tox *tox, int32_t friendnumber)
+int tox_file_data_size(const Tox *tox, int32_t friendnumber)
 {
     return MAX_CRYPTO_DATA_SIZE - 2;
 }
@@ -732,16 +733,17 @@ int tox_file_data_size(Tox *tox, int32_t friendnumber)
  *  return number of bytes remaining to be sent/received on success
  *  return 0 on failure
  */
-uint64_t tox_file_data_remaining(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive)
+uint64_t tox_file_data_remaining(const Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return file_dataremaining(m, friendnumber, filenumber, send_receive);
 }
 
 /***************END OF FILE SENDING FUNCTIONS******************/
 
 /* TODO: expose this properly. */
-static int tox_add_tcp_relay(Tox *tox, const char *address, uint8_t ipv6enabled, uint16_t port, uint8_t *public_key)
+static int tox_add_tcp_relay(Tox *tox, const char *address, uint8_t ipv6enabled, uint16_t port,
+                             const uint8_t *public_key)
 {
     Messenger *m = tox;
     IP_Port ip_port_v64;
@@ -766,7 +768,7 @@ static int tox_add_tcp_relay(Tox *tox, const char *address, uint8_t ipv6enabled,
 }
 
 int tox_bootstrap_from_address(Tox *tox, const char *address,
-                               uint8_t ipv6enabled, uint16_t port, uint8_t *public_key)
+                               uint8_t ipv6enabled, uint16_t port, const uint8_t *public_key)
 {
     Messenger *m = tox;
     tox_add_tcp_relay(tox, address, ipv6enabled, port, public_key);
@@ -776,9 +778,9 @@ int tox_bootstrap_from_address(Tox *tox, const char *address,
 /*  return 0 if we are not connected to the DHT.
  *  return 1 if we are.
  */
-int tox_isconnected(Tox *tox)
+int tox_isconnected(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return DHT_isconnected(m->dht);
 }
 
@@ -823,21 +825,21 @@ void tox_do(Tox *tox)
 /* SAVING AND LOADING FUNCTIONS: */
 
 /*  return size of the messenger data (for saving). */
-uint32_t tox_size(Tox *tox)
+uint32_t tox_size(const Tox *tox)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     return messenger_size(m);
 }
 
 /* Save the messenger in data (must be allocated memory of size Messenger_size()). */
-void tox_save(Tox *tox, uint8_t *data)
+void tox_save(const Tox *tox, uint8_t *data)
 {
-    Messenger *m = tox;
+    const Messenger *m = tox;
     messenger_save(m, data);
 }
 
 /* Load the messenger from data of size length. */
-int tox_load(Tox *tox, uint8_t *data, uint32_t length)
+int tox_load(Tox *tox, const uint8_t *data, uint32_t length)
 {
     Messenger *m = tox;
     return messenger_load(m, data, length);
diff --git a/toxcore/tox.h b/toxcore/tox.h
index afa502f5..5418b03e 100644
--- a/toxcore/tox.h
+++ b/toxcore/tox.h
@@ -82,7 +82,7 @@ typedef struct Tox Tox;
 /*  return TOX_FRIEND_ADDRESS_SIZE byte address to give to others.
  * format: [client_id (32 bytes)][nospam number (4 bytes)][checksum (2 bytes)]
  */
-void tox_get_address(Tox *tox, uint8_t *address);
+void tox_get_address(const Tox *tox, uint8_t *address);
 
 /* Add a friend.
  * Set the data that will be sent along with friend request.
@@ -100,7 +100,7 @@ void tox_get_address(Tox *tox, uint8_t *address);
  *  (the nospam for that friend was set to the new one).
  *  return TOX_FAERR_NOMEM if increasing the friend list size fails.
  */
-int32_t tox_add_friend(Tox *tox, uint8_t *address, uint8_t *data, uint16_t length);
+int32_t tox_add_friend(Tox *tox, const uint8_t *address, const uint8_t *data, uint16_t length);
 
 
 /* Add a friend without sending a friendrequest.
@@ -111,14 +111,14 @@ int32_t tox_add_friend_norequest(Tox *tox, const uint8_t *client_id);
 
 /*  return the friend number associated to that client id.
     return -1 if no such friend */
-int32_t tox_get_friend_number(Tox *tox, uint8_t *client_id);
+int32_t tox_get_friend_number(const Tox *tox, const uint8_t *client_id);
 
 /* Copies the public key associated to that friend id into client_id buffer.
  * Make sure that client_id is of size CLIENT_ID_SIZE.
  *  return 0 if success.
  *  return -1 if failure.
  */
-int tox_get_client_id(Tox *tox, int32_t friendnumber, uint8_t *client_id);
+int tox_get_client_id(const Tox *tox, int32_t friendnumber, uint8_t *client_id);
 
 /* Remove a friend.
  *
@@ -133,14 +133,14 @@ int tox_del_friend(Tox *tox, int32_t friendnumber);
  *  return 0 if friend is not connected to us (Offline).
  *  return -1 on failure.
  */
-int tox_get_friend_connection_status(Tox *tox, int32_t friendnumber);
+int tox_get_friend_connection_status(const Tox *tox, int32_t friendnumber);
 
 /* Checks if there exists a friend with given friendnumber.
  *
  *  return 1 if friend exists.
  *  return 0 if friend doesn't exist.
  */
-int tox_friend_exists(Tox *tox, int32_t friendnumber);
+int tox_friend_exists(const Tox *tox, int32_t friendnumber);
 
 /* Send a text chat message to an online friend.
  *
@@ -157,7 +157,8 @@ int tox_friend_exists(Tox *tox, int32_t friendnumber);
  * however we can generate an id for you by calling plain m_sendmessage.
  */
 uint32_t tox_send_message(Tox *tox, int32_t friendnumber, const uint8_t *message, uint32_t length);
-uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid, uint8_t *message, uint32_t length);
+uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid, const uint8_t *message,
+                                 uint32_t length);
 
 /* Send an action to an online friend.
  *
@@ -173,8 +174,8 @@ uint32_t tox_send_message_withid(Tox *tox, int32_t friendnumber, uint32_t theid,
  *  m_sendaction_withid will send an action message with the id of your choosing,
  *  however we can generate an id for you by calling plain m_sendaction.
  */
-uint32_t tox_send_action(Tox *tox, int32_t friendnumber, uint8_t *action, uint32_t length);
-uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid, uint8_t *action, uint32_t length);
+uint32_t tox_send_action(Tox *tox, int32_t friendnumber, const uint8_t *action, uint32_t length);
+uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid, const uint8_t *action, uint32_t length);
 
 /* Set our nickname.
  * name must be a string of maximum MAX_NAME_LENGTH length.
@@ -184,7 +185,7 @@ uint32_t tox_send_action_withid(Tox *tox, int32_t friendnumber, uint32_t theid,
  *  return 0 if success.
  *  return -1 if failure.
  */
-int tox_set_name(Tox *tox, uint8_t *name, uint16_t length);
+int tox_set_name(Tox *tox, const uint8_t *name, uint16_t length);
 
 /*
  * Get your nickname.
@@ -194,7 +195,7 @@ int tox_set_name(Tox *tox, uint8_t *name, uint16_t length);
  *  return length of name.
  *  return 0 on error.
  */
-uint16_t tox_get_self_name(Tox *tox, uint8_t *name);
+uint16_t tox_get_self_name(const Tox *tox, uint8_t *name);
 
 /* Get name of friendnumber and put it in name.
  * name needs to be a valid memory location with a size of at least MAX_NAME_LENGTH (128) bytes.
@@ -202,13 +203,13 @@ uint16_t tox_get_self_name(Tox *tox, uint8_t *name);
  *  return length of name if success.
  *  return -1 if failure.
  */
-int tox_get_name(Tox *tox, int32_t friendnumber, uint8_t *name);
+int tox_get_name(const Tox *tox, int32_t friendnumber, uint8_t *name);
 
 /*  returns the length of name on success.
  *  returns -1 on failure.
  */
-int tox_get_name_size(Tox *tox, int32_t friendnumber);
-int tox_get_self_name_size(Tox *tox);
+int tox_get_name_size(const Tox *tox, int32_t friendnumber);
+int tox_get_self_name_size(const Tox *tox);
 
 /* Set our user status.
  *
@@ -218,14 +219,14 @@ int tox_get_self_name_size(Tox *tox);
  *  returns 0 on success.
  *  returns -1 on failure.
  */
-int tox_set_status_message(Tox *tox, uint8_t *status, uint16_t length);
+int tox_set_status_message(Tox *tox, const uint8_t *status, uint16_t length);
 int tox_set_user_status(Tox *tox, uint8_t userstatus);
 
 /*  returns the length of status message on success.
  *  returns -1 on failure.
  */
-int tox_get_status_message_size(Tox *tox, int32_t friendnumber);
-int tox_get_self_status_message_size(Tox *tox);
+int tox_get_status_message_size(const Tox *tox, int32_t friendnumber);
+int tox_get_self_status_message_size(const Tox *tox);
 
 /* Copy friendnumber's status message into buf, truncating if size is over maxlen.
  * Get the size you need to allocate from m_get_statusmessage_size.
@@ -234,22 +235,22 @@ int tox_get_self_status_message_size(Tox *tox);
  * returns the length of the copied data on success
  * retruns -1 on failure.
  */
-int tox_get_status_message(Tox *tox, int32_t friendnumber, uint8_t *buf, uint32_t maxlen);
-int tox_get_self_status_message(Tox *tox, uint8_t *buf, uint32_t maxlen);
+int tox_get_status_message(const Tox *tox, int32_t friendnumber, uint8_t *buf, uint32_t maxlen);
+int tox_get_self_status_message(const Tox *tox, uint8_t *buf, uint32_t maxlen);
 
 /*  return one of TOX_USERSTATUS values.
  *  Values unknown to your application should be represented as TOX_USERSTATUS_NONE.
  *  As above, the self variant will return our own TOX_USERSTATUS.
  *  If friendnumber is invalid, this shall return TOX_USERSTATUS_INVALID.
  */
-uint8_t tox_get_user_status(Tox *tox, int32_t friendnumber);
-uint8_t tox_get_self_user_status(Tox *tox);
+uint8_t tox_get_user_status(const Tox *tox, int32_t friendnumber);
+uint8_t tox_get_self_user_status(const Tox *tox);
 
 
 /* returns timestamp of last time friendnumber was seen online, or 0 if never seen.
  * returns -1 on error.
  */
-uint64_t tox_get_last_online(Tox *tox, int32_t friendnumber);
+uint64_t tox_get_last_online(const Tox *tox, int32_t friendnumber);
 
 /* Set our typing status for a friend.
  * You are responsible for turning it on or off.
@@ -264,7 +265,7 @@ int tox_set_user_is_typing(Tox *tox, int32_t friendnumber, uint8_t is_typing);
  * returns 0 if friend is not typing.
  * returns 1 if friend is typing.
  */
-uint8_t tox_get_is_typing(Tox *tox, int32_t friendnumber);
+uint8_t tox_get_is_typing(const Tox *tox, int32_t friendnumber);
 
 /* Sets whether we send read receipts for friendnumber.
  * This function is not lazy, and it will fail if yesno is not (0 or 1).
@@ -274,17 +275,17 @@ void tox_set_sends_receipts(Tox *tox, int32_t friendnumber, int yesno);
 /* Return the number of friends in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_friendlist. */
-uint32_t tox_count_friendlist(Tox *tox);
+uint32_t tox_count_friendlist(const Tox *tox);
 
 /* Return the number of online friends in the instance m. */
-uint32_t tox_get_num_online_friends(Tox *tox);
+uint32_t tox_get_num_online_friends(const Tox *tox);
 
 /* Copy a list of valid friend IDs into the array out_list.
  * If out_list is NULL, returns 0.
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t tox_get_friendlist(Tox *tox, int32_t *out_list, uint32_t list_size);
+uint32_t tox_get_friendlist(const Tox *tox, int32_t *out_list, uint32_t list_size);
 
 /* Set the function that will be executed when a friend request is received.
  *  Function format is function(Tox *tox, uint8_t * public_key, uint8_t * data, uint16_t length, void *userdata)
@@ -295,27 +296,27 @@ void tox_callback_friend_request(Tox *tox, void (*function)(Tox *tox, const uint
 /* Set the function that will be executed when a message from a friend is received.
  *  Function format is: function(Tox *tox, int32_t friendnumber, uint8_t * message, uint32_t length, void *userdata)
  */
-void tox_callback_friend_message(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_friend_message(Tox *tox, void (*function)(Tox *tox, int32_t, const uint8_t *, uint16_t, void *),
                                  void *userdata);
 
 /* Set the function that will be executed when an action from a friend is received.
  *  Function format is: function(Tox *tox, int32_t friendnumber, uint8_t * action, uint32_t length, void *userdata)
  */
-void tox_callback_friend_action(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_friend_action(Tox *tox, void (*function)(Tox *tox, int32_t, const uint8_t *, uint16_t, void *),
                                 void *userdata);
 
 /* Set the callback for name changes.
  *  function(Tox *tox, int32_t friendnumber, uint8_t *newname, uint16_t length, void *userdata)
  *  You are not responsible for freeing newname
  */
-void tox_callback_name_change(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_name_change(Tox *tox, void (*function)(Tox *tox, int32_t, const uint8_t *, uint16_t, void *),
                               void *userdata);
 
 /* Set the callback for status message changes.
  *  function(Tox *tox, int32_t friendnumber, uint8_t *newstatus, uint16_t length, void *userdata)
  *  You are not responsible for freeing newstatus.
  */
-void tox_callback_status_message(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t *, uint16_t, void *),
+void tox_callback_status_message(Tox *tox, void (*function)(Tox *tox, int32_t, const uint8_t *, uint16_t, void *),
                                  void *userdata);
 
 /* Set the callback for status type changes.
@@ -357,7 +358,7 @@ void tox_callback_connection_status(Tox *tox, void (*function)(Tox *tox, int32_t
 
 /* Functions to get/set the nospam part of the id.
  */
-uint32_t tox_get_nospam(Tox *tox);
+uint32_t tox_get_nospam(const Tox *tox);
 void tox_set_nospam(Tox *tox, uint32_t nospam);
 
 
@@ -367,20 +368,20 @@ void tox_set_nospam(Tox *tox, uint32_t nospam);
  *
  *  Function(Tox *tox, int friendnumber, uint8_t *group_public_key, void *userdata)
  */
-void tox_callback_group_invite(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t *, void *), void *userdata);
+void tox_callback_group_invite(Tox *tox, void (*function)(Tox *tox, int32_t, const uint8_t *, void *), void *userdata);
 
 /* Set the callback for group messages.
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * message, uint16_t length, void *userdata)
  */
-void tox_callback_group_message(Tox *tox, void (*function)(Tox *tox, int, int, uint8_t *, uint16_t, void *),
+void tox_callback_group_message(Tox *tox, void (*function)(Tox *tox, int, int, const uint8_t *, uint16_t, void *),
                                 void *userdata);
 
 /* Set the callback for group actions.
  *
  *  Function(Tox *tox, int groupnumber, int friendgroupnumber, uint8_t * action, uint16_t length, void *userdata)
  */
-void tox_callback_group_action(Tox *tox, void (*function)(Tox *tox, int, int, uint8_t *, uint16_t, void *),
+void tox_callback_group_action(Tox *tox, void (*function)(Tox *tox, int, int, const uint8_t *, uint16_t, void *),
                                void *userdata);
 
 /* Set callback function for peer name list changes.
@@ -417,7 +418,7 @@ int tox_del_groupchat(Tox *tox, int groupnumber);
  * return length of name if success
  * return -1 if failure
  */
-int tox_group_peername(Tox *tox, int groupnumber, int peernumber, uint8_t *name);
+int tox_group_peername(const Tox *tox, int groupnumber, int peernumber, uint8_t *name);
 
 /* invite friendnumber to groupnumber
  * return 0 on success
@@ -430,24 +431,24 @@ int tox_invite_friend(Tox *tox, int32_t friendnumber, int groupnumber);
  * returns group number on success
  * returns -1 on failure.
  */
-int tox_join_groupchat(Tox *tox, int32_t friendnumber, uint8_t *friend_group_public_key);
+int tox_join_groupchat(Tox *tox, int32_t friendnumber, const uint8_t *friend_group_public_key);
 
 /* send a group message
  * return 0 on success
  * return -1 on failure
  */
-int tox_group_message_send(Tox *tox, int groupnumber, uint8_t *message, uint32_t length);
+int tox_group_message_send(Tox *tox, int groupnumber, const uint8_t *message, uint32_t length);
 
 /* send a group action
  * return 0 on success
  * return -1 on failure
  */
-int tox_group_action_send(Tox *tox, int groupnumber, uint8_t *action, uint32_t length);
+int tox_group_action_send(Tox *tox, int groupnumber, const uint8_t *action, uint32_t length);
 
 /* Return the number of peers in the group chat on success.
  * return -1 on failure
  */
-int tox_group_number_peers(Tox *tox, int groupnumber);
+int tox_group_number_peers(const Tox *tox, int groupnumber);
 
 /* List all the peers in the group chat.
  *
@@ -459,20 +460,20 @@ int tox_group_number_peers(Tox *tox, int groupnumber);
  *
  * return -1 on failure.
  */
-int tox_group_get_names(Tox *tox, int groupnumber, uint8_t names[][TOX_MAX_NAME_LENGTH], uint16_t lengths[],
+int tox_group_get_names(const Tox *tox, int groupnumber, uint8_t names[][TOX_MAX_NAME_LENGTH], uint16_t lengths[],
                         uint16_t length);
 
 /* Return the number of chats in the instance m.
  * You should use this to determine how much memory to allocate
  * for copy_chatlist. */
-uint32_t tox_count_chatlist(Tox *tox);
+uint32_t tox_count_chatlist(const Tox *tox);
 
 /* Copy a list of valid chat IDs into the array out_list.
  * If out_list is NULL, returns 0.
  * Otherwise, returns the number of elements copied.
  * If the array was too small, the contents
  * of out_list will be truncated to list_size. */
-uint32_t tox_get_chatlist(Tox *tox, int *out_list, uint32_t list_size);
+uint32_t tox_get_chatlist(const Tox *tox, int *out_list, uint32_t list_size);
 
 
 /****************FILE SENDING FUNCTIONS*****************/
@@ -523,8 +524,8 @@ enum {
  *
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length, void *userdata)
  */
-void tox_callback_file_send_request(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, uint64_t, uint8_t *, uint16_t,
-                                    void *), void *userdata);
+void tox_callback_file_send_request(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, uint64_t, const uint8_t *,
+                                    uint16_t, void *), void *userdata);
 
 /* Set the callback for file control requests.
  *
@@ -534,7 +535,7 @@ void tox_callback_file_send_request(Tox *tox, void (*function)(Tox *m, int32_t,
  *  Function(Tox *tox, int32_t friendnumber, uint8_t receive_send, uint8_t filenumber, uint8_t control_type, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void tox_callback_file_control(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, uint8_t, uint8_t, uint8_t *,
+void tox_callback_file_control(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, uint8_t, uint8_t, const uint8_t *,
                                uint16_t, void *), void *userdata);
 
 /* Set the callback for file data.
@@ -542,8 +543,8 @@ void tox_callback_file_control(Tox *tox, void (*function)(Tox *m, int32_t, uint8
  *  Function(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length, void *userdata)
  *
  */
-void tox_callback_file_data(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, uint8_t *, uint16_t length, void *),
-                            void *userdata);
+void tox_callback_file_data(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, const uint8_t *, uint16_t length,
+                            void *), void *userdata);
 
 
 /* Send a file send request.
@@ -551,7 +552,8 @@ void tox_callback_file_data(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t,
  *  return file number on success
  *  return -1 on failure
  */
-int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, uint8_t *filename, uint16_t filename_length);
+int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, const uint8_t *filename,
+                        uint16_t filename_length);
 
 /* Send a file control request.
  *
@@ -562,21 +564,21 @@ int tox_new_file_sender(Tox *tox, int32_t friendnumber, uint64_t filesize, uint8
  *  return -1 on failure
  */
 int tox_file_send_control(Tox *tox, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber, uint8_t message_id,
-                          uint8_t *data, uint16_t length);
+                          const uint8_t *data, uint16_t length);
 
 /* Send file data.
  *
  *  return 0 on success
  *  return -1 on failure
  */
-int tox_file_send_data(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t *data, uint16_t length);
+int tox_file_send_data(Tox *tox, int32_t friendnumber, uint8_t filenumber, const uint8_t *data, uint16_t length);
 
 /* Returns the recommended/maximum size of the filedata you send with tox_file_send_data()
  *
  *  return size on success
  *  return -1 on failure (currently will never return -1)
  */
-int tox_file_data_size(Tox *tox, int32_t friendnumber);
+int tox_file_data_size(const Tox *tox, int32_t friendnumber);
 
 /* Give the number of bytes left to be sent/received.
  *
@@ -585,7 +587,7 @@ int tox_file_data_size(Tox *tox, int32_t friendnumber);
  *  return number of bytes remaining to be sent/received on success
  *  return 0 on failure
  */
-uint64_t tox_file_data_remaining(Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive);
+uint64_t tox_file_data_remaining(const Tox *tox, int32_t friendnumber, uint8_t filenumber, uint8_t send_receive);
 
 /***************END OF FILE SENDING FUNCTIONS******************/
 
@@ -606,12 +608,12 @@ uint64_t tox_file_data_remaining(Tox *tox, int32_t friendnumber, uint8_t filenum
  *  returns 0 otherwise
  */
 int tox_bootstrap_from_address(Tox *tox, const char *address, uint8_t ipv6enabled,
-                               uint16_t port, uint8_t *public_key);
+                               uint16_t port, const uint8_t *public_key);
 
 /*  return 0 if we are not connected to the DHT.
  *  return 1 if we are.
  */
-int tox_isconnected(Tox *tox);
+int tox_isconnected(const Tox *tox);
 
 /*
  *  Run this function at startup.
@@ -645,17 +647,17 @@ void tox_do(Tox *tox);
 /* SAVING AND LOADING FUNCTIONS: */
 
 /*  return size of messenger data (for saving). */
-uint32_t tox_size(Tox *tox);
+uint32_t tox_size(const Tox *tox);
 
 /* Save the messenger in data (must be allocated memory of size Messenger_size()). */
-void tox_save(Tox *tox, uint8_t *data);
+void tox_save(const Tox *tox, uint8_t *data);
 
 /* Load the messenger from data of size length.
  *
  *  returns 0 on success
  *  returns -1 on failure
  */
-int tox_load(Tox *tox, uint8_t *data, uint32_t length);
+int tox_load(Tox *tox, const uint8_t *data, uint32_t length);
 
 #ifdef __cplusplus
 }