Fixes

- Removed void* arithmetic
- Fixed connection_send does not return anything
- Fixed server_events invalid args in main.c (and changed its
  declaration)

connection.c

@@ -265,11 +265,13 @@ void connection_event(int fd, uint32_t events) {
     }
 }
 
-uint32_t connection_send(uint32_t id, const void *data, uint32_t size) {
+uint32_t connection_send(uint32_t id, const void *data_void, uint32_t size) {
+    const char *data = data_void;
     int index = _get_conn_index_by_id(id);
     if (index == -1)
         return 0;
     conn_t *c = _conns[index];
+    uint32_t wrote = 0;
     uint32_t can_write, will_write;
     // write to ring buffer
     can_write = rb_raw_write_size(c->send_buf);
@@ -286,6 +288,7 @@ uint32_t connection_send(uint32_t id, const void *data, uint32_t size) {
         );
         size -= will_write;
         data += will_write;
+        write += will_write;
     }
     // add to epoll if not added
     if (!(c->ev_mask & EPOLLOUT)) {
@@ -299,4 +302,5 @@ uint32_t connection_send(uint32_t id, const void *data, uint32_t size) {
             &ev
         );
     }
+    return wrote;
 }