diff --git a/auto_tests/friends_test.c b/auto_tests/friends_test.c
index 317714d6..3c15b35b 100755
--- a/auto_tests/friends_test.c
+++ b/auto_tests/friends_test.c
@@ -65,13 +65,13 @@ void do_tox(void)
     doMessenger(m);
 }
 
-void parent_confirm_message(Messenger *m, int num, uint8_t *data, uint16_t length)
+void parent_confirm_message(Messenger *m, int num, uint8_t *data, uint16_t length, void* userdata)
 {
     puts("OK");
     request_flags |= SECOND_FLAG;
 }
 
-void parent_confirm_status(Messenger *m, int num, uint8_t *data, uint16_t length)
+void parent_confirm_status(Messenger *m, int num, uint8_t *data, uint16_t length, void* userdata)
 {
     puts("OK");
     request_flags |= FIRST_FLAG;
@@ -108,7 +108,7 @@ int parent_friend_request(void)
     return 0;
 }
 
-void child_got_request(uint8_t *public_key, uint8_t *data, uint16_t length)
+void child_got_request(uint8_t *public_key, uint8_t *data, uint16_t length, void* userdata)
 {
     fputs("OK\nsending status to parent", stdout);
     fflush(stdout);
@@ -116,7 +116,7 @@ void child_got_request(uint8_t *public_key, uint8_t *data, uint16_t length)
     request_flags |= FIRST_FLAG;
 }
 
-void child_got_statuschange(Messenger *m, int friend_num, uint8_t *string, uint16_t length)
+void child_got_statuschange(Messenger *m, int friend_num, uint8_t *string, uint16_t length, void* userdata)
 {
     request_flags |= SECOND_FLAG;
 }
@@ -175,8 +175,8 @@ int main(int argc, char *argv[])
         Messenger_save(m, child_id);
         msync(child_id, crypto_box_PUBLICKEYBYTES, MS_SYNC);
 
-        m_callback_friendrequest(m, child_got_request);
-        m_callback_statusmessage(m, child_got_statuschange);
+        m_callback_friendrequest(m, child_got_request, NULL);
+        m_callback_statusmessage(m, child_got_statuschange, NULL);
 
         /* wait on the friend request */
        while(!(request_flags & FIRST_FLAG))
@@ -207,8 +207,8 @@ int main(int argc, char *argv[])
     m = initMessenger();
 
     msync(parent_id, crypto_box_PUBLICKEYBYTES, MS_SYNC);
-    m_callback_statusmessage(m, parent_confirm_status);
-    m_callback_friendmessage(m, parent_confirm_message);
+    m_callback_statusmessage(m, parent_confirm_status, NULL);
+    m_callback_friendmessage(m, parent_confirm_message, NULL);
 
     /* hacky way to give the child time to set up */
     c_sleep(50);
diff --git a/core/Messenger.c b/core/Messenger.c
index a6189941..ebde5a78 100644
--- a/core/Messenger.c
+++ b/core/Messenger.c
@@ -395,52 +395,59 @@ void m_set_sends_receipts(Messenger *m, int friendnumber, int yesno)
 /* static void (*friend_request)(uint8_t *, uint8_t *, uint16_t);
 static uint8_t friend_request_isset = 0; */
 /* set the function that will be executed when a friend request is received. */
-void m_callback_friendrequest(Messenger *m, void (*function)(uint8_t *, uint8_t *, uint16_t))
+void m_callback_friendrequest(Messenger *m, void (*function)(uint8_t *, uint8_t *, uint16_t, void*), void* userdata)
 {
-    callback_friendrequest(function);
+    callback_friendrequest(function, userdata);
 }
 
 /* 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, int, uint8_t *, uint16_t))
+void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata)
 {
     m->friend_message = function;
     m->friend_message_isset = 1;
+    m->friend_message_userdata = userdata;
 }
 
-void m_callback_action(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t))
+void m_callback_action(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata)
 {
     m->friend_action = function;
     m->friend_action_isset = 1;
+    m->friend_action_userdata = userdata;
 }
 
-void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t))
+void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata)
 {
     m->friend_namechange = function;
     m->friend_namechange_isset = 1;
+    m->friend_namechange_userdata = userdata;
 }
 
-void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t))
+void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata)
 {
     m->friend_statusmessagechange = function;
     m->friend_statusmessagechange_isset = 1;
+    m->friend_statuschange_userdata = userdata;
 }
 
-void m_callback_userstatus(Messenger *m, void (*function)(Messenger *m, int, USERSTATUS))
+void m_callback_userstatus(Messenger *m, void (*function)(Messenger *m, int, USERSTATUS, void*), void* userdata)
 {
     m->friend_userstatuschange = function;
     m->friend_userstatuschange_isset = 1;
+    m->friend_userstatuschange_userdata = userdata;
 }
 
-void m_callback_read_receipt(Messenger *m, void (*function)(Messenger *m, int, uint32_t))
+void m_callback_read_receipt(Messenger *m, void (*function)(Messenger *m, int, uint32_t, void*), void* userdata)
 {
     m->read_receipt = function;
     m->read_receipt_isset = 1;
+    m->read_receipt_userdata = userdata;
 }
 
-void m_callback_connectionstatus(Messenger *m, void (*function)(Messenger *m, int, uint8_t))
+void m_callback_connectionstatus(Messenger *m, void (*function)(Messenger *m, int, uint8_t, void*), void* userdata)
 {
     m->friend_connectionstatuschange = function;
     m->friend_connectionstatuschange_isset = 1;
+    m->friend_connectionstatuschange_userdata = userdata;
 }
 
 static void check_friend_connectionstatus(Messenger *m, int friendnumber, uint8_t status)
@@ -452,7 +459,7 @@ static void check_friend_connectionstatus(Messenger *m, int friendnumber, uint8_
     const uint8_t was_connected = m->friendlist[friendnumber].status == FRIEND_ONLINE;
     const uint8_t is_connected = status == FRIEND_ONLINE;
     if (is_connected != was_connected)
-        m->friend_connectionstatuschange(m, friendnumber, is_connected);
+        m->friend_connectionstatuschange(m, friendnumber, is_connected, m->friend_connectionstatuschange_userdata);
 }
 
 void set_friend_status(Messenger *m, int friendnumber, uint8_t status)
@@ -569,7 +576,7 @@ void doFriends(Messenger *m)
                     if (data_length >= MAX_NAME_LENGTH || data_length == 0)
                         break;
                     if(m->friend_namechange_isset)
-                        m->friend_namechange(m, i, data, data_length);
+                        m->friend_namechange(m, i, data, data_length, m->friend_namechange_userdata);
                     memcpy(m->friendlist[i].name, data, data_length);
                     m->friendlist[i].name[data_length - 1] = 0; /* make sure the NULL terminator is present. */
                     break;
@@ -580,7 +587,8 @@ void doFriends(Messenger *m)
                     uint8_t *status = calloc(MIN(data_length, MAX_STATUSMESSAGE_LENGTH), 1);
                     memcpy(status, data, MIN(data_length, MAX_STATUSMESSAGE_LENGTH));
                     if (m->friend_statusmessagechange_isset)
-                        m->friend_statusmessagechange(m, i, status, MIN(data_length, MAX_STATUSMESSAGE_LENGTH));
+                        m->friend_statusmessagechange(m, i, status, MIN(data_length, MAX_STATUSMESSAGE_LENGTH),
+                                                      m->friend_statuschange_userdata);
                     set_friend_statusmessage(m, i, status, MIN(data_length, MAX_STATUSMESSAGE_LENGTH));
                     free(status);
                     break;
@@ -590,7 +598,7 @@ void doFriends(Messenger *m)
                         break;
                     USERSTATUS status = data[0];
                     if (m->friend_userstatuschange_isset)
-                        m->friend_userstatuschange(m, i, status);
+                        m->friend_userstatuschange(m, i, status, m->friend_userstatuschange_userdata);
                     set_friend_userstatus(m, i, status);
                     break;
                 }
@@ -603,12 +611,12 @@ void doFriends(Messenger *m)
                         write_cryptpacket_id(m, i, PACKET_ID_RECEIPT, message_id, message_id_length);
                     }
                     if (m->friend_message_isset)
-                        (*m->friend_message)(m, i, message, message_length);
+                        (*m->friend_message)(m, i, message, message_length, m->friend_message_userdata);
                     break;
                 }
                 case PACKET_ID_ACTION: {
                     if (m->friend_action_isset)
-                        (*m->friend_action)(m, i, data, data_length);
+                        (*m->friend_action)(m, i, data, data_length, m->friend_action_userdata);
                     break;
                 }
                 case PACKET_ID_RECEIPT: {
@@ -618,7 +626,7 @@ void doFriends(Messenger *m)
                     memcpy(&msgid, data, sizeof(msgid));
                     msgid = ntohl(msgid);
                     if (m->read_receipt_isset)
-                        (*m->read_receipt)(m, i, msgid);
+                        (*m->read_receipt)(m, i, msgid, m->read_receipt_userdata);
                     break;
                 }
                 }
diff --git a/core/Messenger.h b/core/Messenger.h
index 36e24596..fa69d104 100644
--- a/core/Messenger.h
+++ b/core/Messenger.h
@@ -105,22 +105,30 @@ typedef struct Messenger {
     Friend *friendlist;
     uint32_t numfriends;
 
-    void (*friend_message)(struct Messenger *m, int, uint8_t *, uint16_t);
+    void (*friend_message)(struct Messenger *m, int, uint8_t *, uint16_t, void*);
     uint8_t friend_message_isset;
-    void (*friend_action)(struct Messenger *m, int, uint8_t *, uint16_t);
+    void* friend_message_userdata;
+    void (*friend_action)(struct Messenger *m, int, uint8_t *, uint16_t, void*);
     uint8_t friend_action_isset;
-    void (*friend_namechange)(struct Messenger *m, int, uint8_t *, uint16_t);
+    void* friend_action_userdata;
+    void (*friend_namechange)(struct Messenger *m, int, uint8_t *, uint16_t, void*);
     uint8_t friend_namechange_isset;
-    void (*friend_statusmessagechange)(struct Messenger *m, int, uint8_t *, uint16_t);
+    void* friend_namechange_userdata;
+    void (*friend_statusmessagechange)(struct Messenger *m, int, uint8_t *, uint16_t, void*);
     uint8_t friend_statusmessagechange_isset;
-    void (*friend_userstatuschange)(struct Messenger *m, int, USERSTATUS);
+    void* friend_statusmessagechange_userdata;
+    void (*friend_userstatuschange)(struct Messenger *m, int, USERSTATUS, void*);
     uint8_t friend_userstatuschange_isset;
-    void (*read_receipt)(struct Messenger *m, int, uint32_t);
+    void* friend_userstatuschange_userdata;
+    void (*read_receipt)(struct Messenger *m, int, uint32_t, void*);
     uint8_t read_receipt_isset;
-    void (*friend_statuschange)(struct Messenger *m, int, uint8_t);
+    void* read_receipt_userdata;
+    void (*friend_statuschange)(struct Messenger *m, int, uint8_t, void*);
     uint8_t friend_statuschange_isset;
-    void (*friend_connectionstatuschange)(struct Messenger *m, int, uint8_t);
+    void* friend_statuschange_userdata;
+    void (*friend_connectionstatuschange)(struct Messenger *m, int, uint8_t, void*);
     uint8_t friend_connectionstatuschange_isset;
+    void* friend_connectionstatuschange_userdata;
 
 
 } Messenger;
@@ -230,29 +238,29 @@ void m_set_sends_receipts(Messenger *m, int friendnumber, int yesno);
 
 /* set the function that will be executed when a friend request is received.
     function format is function(uint8_t * public_key, uint8_t * data, uint16_t length) */
-void m_callback_friendrequest(Messenger *m, void (*function)(uint8_t *, uint8_t *, uint16_t));
+void m_callback_friendrequest(Messenger *m, void (*function)(uint8_t *, uint8_t *, uint16_t, void*), void* userdata);
 
 /* set the function that will be executed when a message from a friend is received.
     function format is: function(int friendnumber, uint8_t * message, uint32_t length) */
-void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t));
+void m_callback_friendmessage(Messenger *m, void (*function)(Messenger *m, int, 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(int friendnumber, uint8_t * action, uint32_t length) */
-void m_callback_action(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t));
+void m_callback_action(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata);
 
 /* set the callback for name changes
     function(int friendnumber, uint8_t *newname, uint16_t length)
     you are not responsible for freeing newname */
-void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t));
+void m_callback_namechange(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata);
 
 /* set the callback for status message changes
     function(int friendnumber, uint8_t *newstatus, uint16_t length)
     you are not responsible for freeing newstatus */
-void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t));
+void m_callback_statusmessage(Messenger *m, void (*function)(Messenger *m, int, uint8_t *, uint16_t, void*), void* userdata);
 
 /* set the callback for status type changes
     function(int friendnumber, USERSTATUS kind) */
-void m_callback_userstatus(Messenger *m, void (*function)(Messenger *m, int, USERSTATUS));
+void m_callback_userstatus(Messenger *m, void (*function)(Messenger *m, int, USERSTATUS, void*), void* userdata);
 
 /* set the callback for read receipts
     function(int friendnumber, uint32_t receipt)
@@ -261,7 +269,7 @@ void m_callback_userstatus(Messenger *m, void (*function)(Messenger *m, int, USE
     has been received on the other side. since core doesn't
     track ids for you, receipt may not correspond to any message
     in that case, you should discard it. */
-void m_callback_read_receipt(Messenger *m, void (*function)(Messenger *m, int, uint32_t));
+void m_callback_read_receipt(Messenger *m, void (*function)(Messenger *m, int, uint32_t, void*), void* userdata);
 
 /* set the callback for connection status changes
     function(int friendnumber, uint8_t status)
@@ -271,7 +279,7 @@ void m_callback_read_receipt(Messenger *m, void (*function)(Messenger *m, int, u
     note that this callback is not called when adding friends, thus the "after
     being previously online" part. it's assumed that when adding friends,
     their connection status is offline. */
-void m_callback_connectionstatus(Messenger *m, void (*function)(Messenger *m, int, uint8_t));
+void m_callback_connectionstatus(Messenger *m, void (*function)(Messenger *m, int, uint8_t, void*), void* userdata);
 
 /* run this at startup
  *  returns allocated instance of Messenger on success
diff --git a/core/friend_requests.c b/core/friend_requests.c
index 422cc028..5e9b447c 100644
--- a/core/friend_requests.c
+++ b/core/friend_requests.c
@@ -57,14 +57,15 @@ int send_friendrequest(uint8_t * public_key, uint8_t * data, uint32_t length)
     return num;
 }
 
-static void (*handle_friendrequest)(uint8_t *, uint8_t *, uint16_t);
+static void (*handle_friendrequest)(uint8_t *, uint8_t *, uint16_t, void*);
 static uint8_t handle_friendrequest_isset = 0;
-
+static void* handle_friendrequest_userdata;
 /* set the function that will be executed when a friend request is received. */
-void callback_friendrequest(void (*function)(uint8_t *, uint8_t *, uint16_t))
+void callback_friendrequest(void (*function)(uint8_t *, uint8_t *, uint16_t, void*), void* userdata)
 {
     handle_friendrequest = function;
     handle_friendrequest_isset = 1;
+    handle_friendrequest_userdata = userdata;
 }
 
 
@@ -121,7 +122,7 @@ static int friendreq_handlepacket(IP_Port source, uint8_t * packet, uint32_t len
                 return 1;
 
             addto_receivedlist(public_key);
-            (*handle_friendrequest)(public_key, data, len);
+            (*handle_friendrequest)(public_key, data, len, handle_friendrequest_userdata);
         } else { /* if request is not for us, try routing it. */
             if(route_packet(packet + 1, packet, length) == length)
                 return 0;
diff --git a/core/friend_requests.h b/core/friend_requests.h
index 708d8f66..f18107ce 100644
--- a/core/friend_requests.h
+++ b/core/friend_requests.h
@@ -37,7 +37,7 @@ int send_friendrequest(uint8_t *public_key, uint8_t *data, uint32_t length);
 
 /* set the function that will be executed when a friend request for us is received.
     function format is function(uint8_t * public_key, uint8_t * data, uint16_t length) */
-void callback_friendrequest(void (*function)(uint8_t *, uint8_t *, uint16_t));
+void callback_friendrequest(void (*function)(uint8_t *, uint8_t *, uint16_t, void*), void* userdata);
 
 /* sets up friendreq packet handlers */
 void friendreq_init(void);
diff --git a/testing/Messenger_test.c b/testing/Messenger_test.c
index 51542c6d..fa5d6890 100644
--- a/testing/Messenger_test.c
+++ b/testing/Messenger_test.c
@@ -55,7 +55,7 @@
  * networking_requesthandler and so cannot take a Messenger * */
 static Messenger *m;
 
-void print_request(uint8_t * public_key, uint8_t * data, uint16_t length)
+void print_request(uint8_t * public_key, uint8_t * data, uint16_t length, void* userdata)
 {
     printf("Friend request received from: \n");
     printf("ClientID: ");
@@ -80,7 +80,7 @@ void print_request(uint8_t * public_key, uint8_t * data, uint16_t length)
     }
 }
 
-void print_message(Messenger *m, int friendnumber, uint8_t * string, uint16_t length)
+void print_message(Messenger *m, int friendnumber, 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);
@@ -114,8 +114,8 @@ int main(int argc, char *argv[])
         fclose(file);
 
     }
-    m_callback_friendrequest(m, print_request);
-    m_callback_friendmessage(m, print_message);
+    m_callback_friendrequest(m, print_request, NULL);
+    m_callback_friendmessage(m, print_message, NULL);
 
     printf("OUR ID: ");
     uint32_t i;
diff --git a/testing/nTox.c b/testing/nTox.c
index 1322067e..59d1cbf6 100644
--- a/testing/nTox.c
+++ b/testing/nTox.c
@@ -336,7 +336,7 @@ void do_refresh()
     refresh();
 }
 
-void print_request(uint8_t *public_key, uint8_t *data, uint16_t length)
+void print_request(uint8_t *public_key, uint8_t *data, uint16_t length, void* userdata)
 {
     new_lines("[i] received friend request with message:");
     new_lines((char *)data);
@@ -349,12 +349,12 @@ void print_request(uint8_t *public_key, uint8_t *data, uint16_t length)
     do_refresh();
 }
 
-void print_message(Messenger *m, int friendnumber, uint8_t * string, uint16_t length)
+void print_message(Messenger *m, int friendnumber, uint8_t * string, uint16_t length, void* userdata)
 {
     new_lines(format_message(m, (char*)string, friendnumber));
 }
 
-void print_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void print_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
     char name[MAX_NAME_LENGTH];
     if(getname(m, friendnumber, (uint8_t*)name) != -1) {
@@ -364,7 +364,7 @@ void print_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t
     }
 }
 
-void print_statuschange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void print_statuschange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
     char name[MAX_NAME_LENGTH];
     if(getname(m, friendnumber, (uint8_t*)name) != -1) {
@@ -467,10 +467,10 @@ int main(int argc, char *argv[])
 
     load_key(m, filename);
 
-    m_callback_friendrequest(m, print_request);
-    m_callback_friendmessage(m, print_message);
-    m_callback_namechange(m, print_nickchange);
-    m_callback_statusmessage(m, print_statuschange);
+    m_callback_friendrequest(m, print_request, NULL);
+    m_callback_friendmessage(m, print_message, NULL);
+    m_callback_namechange(m, print_nickchange, NULL);
+    m_callback_statusmessage(m, print_statuschange, NULL);
 
     initscr();
     noecho();
diff --git a/testing/toxic/main.c b/testing/toxic/main.c
index b6eadf2e..397f9391 100644
--- a/testing/toxic/main.c
+++ b/testing/toxic/main.c
@@ -46,7 +46,7 @@ int w_num;
 int active_window;
 
 /* CALLBACKS START */
-void on_request(uint8_t *public_key, uint8_t *data, uint16_t length)
+void on_request(uint8_t *public_key, uint8_t *data, uint16_t length, void* userdata)
 {
   int n = add_req(public_key);
   wprintw(prompt->window, "\nFriend request from:\n");
@@ -65,7 +65,7 @@ void on_request(uint8_t *public_key, uint8_t *data, uint16_t length)
   }
 }
 
-void on_message(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void on_message(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
   int i;
   for (i = 0; i < MAX_WINDOW_SLOTS; ++i) {
@@ -74,7 +74,7 @@ void on_message(Messenger *m, int friendnumber, uint8_t *string, uint16_t length
   }
 }
 
-void on_action(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void on_action(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
   int i;
   for (i = 0; i < MAX_WINDOW_SLOTS; ++i) {
@@ -83,7 +83,7 @@ void on_action(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
   }
 }
 
-void on_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void on_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
   wprintw(prompt->window, "\n(nickchange) %d: %s\n", friendnumber, string);
   int i;
@@ -93,7 +93,7 @@ void on_nickchange(Messenger *m, int friendnumber, uint8_t *string, uint16_t len
   }
 }
 
-void on_statuschange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length)
+void on_statuschange(Messenger *m, int friendnumber, uint8_t *string, uint16_t length, void* userdata)
 {
   wprintw(prompt->window, "\n(statuschange) %d: %s\n", friendnumber, string);
   int i;
@@ -134,11 +134,11 @@ static void init_tox()
   m = initMessenger();
 
   /* Callbacks */
-  m_callback_friendrequest(m, on_request);
-  m_callback_friendmessage(m, on_message);
-  m_callback_namechange(m, on_nickchange);
-  m_callback_statusmessage(m, on_statuschange);
-  m_callback_action(m, on_action);
+  m_callback_friendrequest(m, on_request, NULL);
+  m_callback_friendmessage(m, on_message, NULL);
+  m_callback_namechange(m, on_nickchange, NULL);
+  m_callback_statusmessage(m, on_statuschange, NULL);
+  m_callback_action(m, on_action, NULL);
 }
 
 #define MAXLINE 90    /* Approx max number of chars in a sever line (IP + port + key) */