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/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/toxcore/Messenger.c b/toxcore/Messenger.c
index 22b5cd95..65f00f30 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -40,10 +40,10 @@
 
 
 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 +109,7 @@ 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 +125,7 @@ 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 +142,7 @@ 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 +152,7 @@ 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 +183,7 @@ 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 +346,7 @@ 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 +354,7 @@ 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 +402,7 @@ 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 +419,7 @@ 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 +434,7 @@ 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 +447,7 @@ 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 +492,7 @@ 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 +509,7 @@ 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 +518,7 @@ 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 +526,7 @@ 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 +565,7 @@ 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 +576,7 @@ 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 +591,12 @@ 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 +604,7 @@ 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 +618,12 @@ 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 +647,7 @@ 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 +655,23 @@ 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 +681,7 @@ 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 +700,7 @@ 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 +713,12 @@ 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 +745,28 @@ 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 +804,7 @@ 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 +840,7 @@ 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 +862,7 @@ 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 +880,7 @@ 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 +904,7 @@ 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 +921,7 @@ 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 +931,7 @@ 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 +942,7 @@ 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 +961,7 @@ 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;
 
@@ -1141,7 +1141,7 @@ 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 +1189,7 @@ 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 +1222,7 @@ 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 +1237,7 @@ 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 +1251,7 @@ 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 +1269,7 @@ 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 +1315,7 @@ 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;
@@ -1327,7 +1327,7 @@ 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 *,
+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;
@@ -1339,7 +1339,7 @@ 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;
@@ -1353,7 +1353,7 @@ 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,
+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))
@@ -1376,7 +1376,7 @@ 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 +1406,8 @@ 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 +1494,7 @@ 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 +1529,7 @@ 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 +1552,7 @@ 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 +1565,7 @@ 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 +1655,7 @@ 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 +1667,12 @@ 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 +1687,7 @@ 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 +1703,7 @@ 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 +1717,7 @@ 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 +1738,7 @@ 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 +1755,7 @@ 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 +1772,7 @@ 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 +2029,13 @@ 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 +2054,13 @@ 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 +2128,8 @@ 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 +2216,7 @@ 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 +2337,7 @@ 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;
 
@@ -2530,12 +2530,12 @@ 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 +2614,7 @@ 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 +2639,7 @@ 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 +2776,7 @@ 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 +2796,7 @@ 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 +2811,7 @@ 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 +2821,7 @@ 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 +2853,7 @@ 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 +2883,7 @@ 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 +2902,7 @@ 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..7bac8bf6 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 +344,8 @@ 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 +355,7 @@ 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 +375,7 @@ 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 +383,13 @@ 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 +403,8 @@ 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 +413,21 @@ 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 +442,7 @@ 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 +458,20 @@ 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 +479,7 @@ 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 +526,20 @@ 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.
@@ -583,24 +583,24 @@ 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 +612,7 @@ 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 +621,7 @@ 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.
@@ -629,7 +629,7 @@ 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 *,
+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.
@@ -637,7 +637,7 @@ 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);
 
 /* Send a file send request.
@@ -645,7 +645,7 @@ 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,
+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.
@@ -653,7 +653,7 @@ 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);
 
 /* 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 +661,15 @@ 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 +678,7 @@ 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 +686,7 @@ 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 +694,7 @@ 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 +704,14 @@ 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 +722,14 @@ 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 +756,28 @@ 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 +785,18 @@ 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..623c48dc 100644
--- a/toxcore/TCP_client.c
+++ b/toxcore/TCP_client.c
@@ -65,7 +65,7 @@ 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);
@@ -335,8 +335,8 @@ 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;
diff --git a/toxcore/TCP_client.h b/toxcore/TCP_client.h
index afb95392..90c79180 100644
--- a/toxcore/TCP_client.h
+++ b/toxcore/TCP_client.h
@@ -79,8 +79,8 @@ typedef struct  {
 
 /* 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
  */
diff --git a/toxcore/net_crypto.c b/toxcore/net_crypto.c
index 15487f37..4dce8391 100644
--- a/toxcore/net_crypto.c
+++ b/toxcore/net_crypto.c
@@ -751,7 +751,7 @@ static int send_data_packet(Net_Crypto *c, int crypt_connection_id, uint8_t *dat
  * 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)
+                                   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(Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_DATA_SIZE)
         return -1;
@@ -1317,7 +1317,7 @@ 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(Net_Crypto *c, const uint8_t *public_key)
 {
     uint32_t i;
 
@@ -1493,7 +1493,7 @@ 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);
 
@@ -1790,7 +1790,7 @@ 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(Net_Crypto *c, const uint8_t *public_key)
 {
     uint32_t i;
 
@@ -1825,7 +1825,7 @@ 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);
 
@@ -1878,7 +1878,7 @@ 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;
@@ -2119,7 +2119,7 @@ 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);
 
@@ -2390,7 +2390,7 @@ 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(Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0)
         return -1;
@@ -2427,7 +2427,7 @@ 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(Net_Crypto *c, int crypt_connection_id, const uint8_t *data, uint32_t length)
 {
     if (length == 0 || length > MAX_CRYPTO_DATA_SIZE)
         return -1;
diff --git a/toxcore/net_crypto.h b/toxcore/net_crypto.h
index 82d454d3..178a83b6 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;
 
@@ -220,7 +220,7 @@ 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);
 
 /* Copy friends DHT public key into dht_key.
  *
@@ -279,7 +279,7 @@ 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);
 
 /* returns the number of packet slots left in the sendbuffer.
  * return 0 if failure.
@@ -293,28 +293,28 @@ 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(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(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.
diff --git a/toxcore/onion_client.c b/toxcore/onion_client.c
index 40701e2d..be06e1c7 100644
--- a/toxcore/onion_client.c
+++ b/toxcore/onion_client.c
@@ -851,7 +851,7 @@ 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;
diff --git a/toxcore/onion_client.h b/toxcore/onion_client.h
index a74783f6..1f15d4bf 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;
@@ -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
diff --git a/toxcore/tox.c b/toxcore/tox.c
index 79e4c042..129f2b07 100644
--- a/toxcore/tox.c
+++ b/toxcore/tox.c
@@ -373,7 +373,7 @@ 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 +383,7 @@ 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 +394,7 @@ 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 +405,7 @@ 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;
@@ -486,7 +486,7 @@ 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 +496,7 @@ 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 +507,7 @@ 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;
@@ -651,7 +651,7 @@ 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 *,
+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)
 {
@@ -663,7 +663,7 @@ 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 *,
+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;
@@ -674,7 +674,7 @@ 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 tox_callback_file_data(Tox *tox, void (*function)(Messenger *tox, int32_t, uint8_t, const uint8_t *, uint16_t length,
                             void *),
                             void *userdata)
 
diff --git a/toxcore/tox.h b/toxcore/tox.h
index afa502f5..65088ebb 100644
--- a/toxcore/tox.h
+++ b/toxcore/tox.h
@@ -295,27 +295,27 @@ 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.
@@ -367,20 +367,20 @@ 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.
@@ -523,7 +523,7 @@ 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 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 +534,7 @@ 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.
@@ -542,7 +542,7 @@ 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 tox_callback_file_data(Tox *tox, void (*function)(Tox *m, int32_t, uint8_t, const uint8_t *, uint16_t length, void *),
                             void *userdata);