diff --git a/examples/arduino/teensy41-http/teensy41-http.ino b/examples/arduino/teensy41-http/teensy41-http.ino
index f9368630..90a6d54e 100644
--- a/examples/arduino/teensy41-http/teensy41-http.ino
+++ b/examples/arduino/teensy41-http/teensy41-http.ino
@@ -25,7 +25,7 @@ uint64_t mg_millis(void) {  // Let Mongoose use our uptime function
 // Simple HTTP server that runs on port 8000
 // Mongoose event handler function, gets called by the mg_mgr_poll()
 // See https://mongoose.ws/documentation/#2-minute-integration-guide
-static void simple_http_listener(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void simple_http_listener(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     // The MG_EV_HTTP_MSG event means HTTP request. `hm` holds parsed request,
     // see https://mongoose.ws/documentation/#struct-mg_http_message
diff --git a/examples/arduino/w5500-http/w5500-http.ino b/examples/arduino/w5500-http/w5500-http.ino
index 93959785..abf3fe75 100644
--- a/examples/arduino/w5500-http/w5500-http.ino
+++ b/examples/arduino/w5500-http/w5500-http.ino
@@ -38,7 +38,7 @@ void setup() {
   // Setup HTTP listener. Respond "ok" on any HTTP request
   mg_http_listen(
       &mgr, "http://0.0.0.0",
-      [](struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+      [](struct mg_connection *c, int ev, void *ev_data) {
         if (ev == MG_EV_HTTP_MSG) mg_http_reply(c, 200, "", "ok\n");
       },
       &mgr);
diff --git a/examples/arduino/w5500-mqtt/net.c b/examples/arduino/w5500-mqtt/net.c
index 07f90dd9..e756410b 100644
--- a/examples/arduino/w5500-mqtt/net.c
+++ b/examples/arduino/w5500-mqtt/net.c
@@ -15,7 +15,7 @@ void mqtt_publish(const char *message) {
   if (mqtt_connection) mg_mqtt_pub(mqtt_connection, &opts);
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_MQTT_OPEN) {
     MG_INFO(("%lu CONNECTED to %s", c->id, MQTT_SERVER));
     struct mg_mqtt_opts opts = {};
diff --git a/examples/captive-dns-server/main.c b/examples/captive-dns-server/main.c
index e69e501b..db60f53e 100644
--- a/examples/captive-dns-server/main.c
+++ b/examples/captive-dns-server/main.c
@@ -20,7 +20,7 @@ uint8_t answer[] = {
     1,    2,    3, 4     // 4 bytes - IP address
 };
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     c->is_hexdumping = 1;
   } else if (ev == MG_EV_READ) {
@@ -41,7 +41,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     }
     mg_iobuf_del(&c->recv, 0, c->recv.len);
   }
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/examples/device-dashboard/net.c b/examples/device-dashboard/net.c
index 91d29511..2d8d3b1c 100644
--- a/examples/device-dashboard/net.c
+++ b/examples/device-dashboard/net.c
@@ -51,7 +51,7 @@ int ui_event_next(int no, struct ui_event *e) {
 
 // SNTP connection event handler. When we get a response from an SNTP server,
 // adjust s_boot_timestamp. We'll get a valid time from that point on
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   uint64_t *expiration_time = (uint64_t *) c->data;
   if (ev == MG_EV_OPEN) {
     *expiration_time = mg_millis() + 3000;  // Store expiration time in 3s
@@ -62,7 +62,6 @@ static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_POLL) {
     if (mg_millis() > *expiration_time) c->is_closing = 1;
   }
-  (void) fn_data;
 }
 
 static void timer_sntp_fn(void *param) {  // SNTP timer function. Sync up time
@@ -262,9 +261,9 @@ static void handle_device_eraselast(struct mg_connection *c) {
 }
 
 // HTTP request handler function
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ACCEPT) {
-    if (fn_data != NULL) {  // TLS listener!
+    if (c->fn_data != NULL) {  // TLS listener!
       struct mg_tls_opts opts = {0};
       opts.cert = mg_unpacked("/certs/server_cert.pem");
       opts.key = mg_unpacked("/certs/server_key.pem");
diff --git a/examples/embedded-filesystem/main.c b/examples/embedded-filesystem/main.c
index 3a42fdf3..c1813266 100644
--- a/examples/embedded-filesystem/main.c
+++ b/examples/embedded-filesystem/main.c
@@ -6,7 +6,7 @@
 const char *s_listening_url = "http://0.0.0.0:8000";
 
 // HTTP request handler function
-void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_serve_opts opts = {
         .root_dir = "/web_root",
@@ -14,7 +14,6 @@ void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       };
     mg_http_serve_dir(c, ev_data, &opts);
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/esp32/micropython/mongoose/main.c b/examples/esp32/micropython/mongoose/main.c
index 6a72d005..fa2914a2 100644
--- a/examples/esp32/micropython/mongoose/main.c
+++ b/examples/esp32/micropython/mongoose/main.c
@@ -8,9 +8,8 @@ static void t_fn(void *arg) {  // Tick periodically
   (void) arg;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) mg_http_reply(c, 200, "", "hi\n");
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/examples/esp8266/http-client-server/src/main/main.c b/examples/esp8266/http-client-server/src/main/main.c
index 8399f37d..6aa027e8 100644
--- a/examples/esp8266/http-client-server/src/main/main.c
+++ b/examples/esp8266/http-client-server/src/main/main.c
@@ -9,8 +9,8 @@
 #define SERVER_URL "http://0.0.0.0:80"
 #define CLIENT_URL "http://info.cern.ch"
 
-// Event handler for an server (accepted) connection
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+// Event handler for a server (accepted) connection
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     mg_http_reply(c, 200, "", "Hello from ESP!\n");
   }
@@ -20,7 +20,7 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
 // To enable TLS for HTTP,
 //   1. Copy "ca.pem" file to the ESP8266 flash FS
 //   2. Add TLS init snippet for the connection, see examples/http-client
-static void cb2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb2(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_CONNECT) {
     struct mg_str s = mg_url_host(CLIENT_URL);
     mg_printf(c, "GET / HTTP/1.0\r\nHost: %.*s\r\n\r\n", (int) s.len, s.ptr);
diff --git a/examples/file-upload-html-form/main.c b/examples/file-upload-html-form/main.c
index 8fa06e20..ce08a515 100644
--- a/examples/file-upload-html-form/main.c
+++ b/examples/file-upload-html-form/main.c
@@ -16,7 +16,7 @@
 //
 // Also, consider changing -DMG_IO_SIZE=SOME_BIG_VALUE to increase IO buffer
 // increment when reading data.
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     MG_INFO(("New request to: [%.*s], body size: %lu", (int) hm->uri.len,
@@ -35,7 +35,6 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/file-upload-multiple-posts/main.c b/examples/file-upload-multiple-posts/main.c
index b1b8c4b9..8895da52 100644
--- a/examples/file-upload-multiple-posts/main.c
+++ b/examples/file-upload-multiple-posts/main.c
@@ -6,7 +6,7 @@
 // HTTP request handler function. It implements the following endpoints:
 //   /upload - Saves the next file chunk
 //   all other URI - serves web_root/ directory
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/upload")) {
@@ -25,7 +25,6 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/file-upload-single-post/main.c b/examples/file-upload-single-post/main.c
index 982e918e..b9bd6423 100644
--- a/examples/file-upload-single-post/main.c
+++ b/examples/file-upload-single-post/main.c
@@ -11,7 +11,7 @@
 // HTTP request handler function. It implements the following endpoints:
 //   /upload - Saves the next file chunk
 //   all other URI - serves web_root/ directory
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     // Parse the incoming data ourselves. If we can parse the request,
     // store two size_t variables in the c->data: expected len and recv len.
@@ -38,7 +38,7 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       }
     }
   }
-  (void) fn_data, (void) ev_data;
+  (void) ev_data;
 }
 
 int main(void) {
diff --git a/examples/http-client/main.c b/examples/http-client/main.c
index a1f76cdd..965b2207 100644
--- a/examples/http-client/main.c
+++ b/examples/http-client/main.c
@@ -15,7 +15,7 @@ static const char *s_post_data = NULL;      // POST data
 static const uint64_t s_timeout_ms = 1500;  // Connect timeout in milliseconds
 
 // Print HTTP response and signal that we're done
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // Connection created. Store connect expiration time in c->data
     *(uint64_t *) c->data = mg_millis() + s_timeout_ms;
@@ -50,9 +50,9 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     printf("%.*s", (int) hm->message.len, hm->message.ptr);
     c->is_draining = 1;        // Tell mongoose to close this connection
-    *(bool *) fn_data = true;  // Tell event loop to stop
+    *(bool *) c->fn_data = true;  // Tell event loop to stop
   } else if (ev == MG_EV_ERROR) {
-    *(bool *) fn_data = true;  // Error, tell event loop to stop
+    *(bool *) c->fn_data = true;  // Error, tell event loop to stop
   }
 }
 
diff --git a/examples/http-proxy-client/main.c b/examples/http-proxy-client/main.c
index 35adb96b..aea5d000 100644
--- a/examples/http-proxy-client/main.c
+++ b/examples/http-proxy-client/main.c
@@ -10,8 +10,8 @@
 #include "mongoose.h"
 
 // Print HTTP response and signal that we're done
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  const char *url = fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  const char *url = c->fn_data;
   static bool connected;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
diff --git a/examples/http-restful-server/main.c b/examples/http-restful-server/main.c
index 9e2b76d4..b00c5d1e 100644
--- a/examples/http-restful-server/main.c
+++ b/examples/http-restful-server/main.c
@@ -56,8 +56,8 @@ static const char *s_tls_key =
 
 // We use the same event handler function for HTTP and HTTPS connections
 // fn_data is NULL for plain HTTP, and non-NULL for HTTPS
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  if (ev == MG_EV_ACCEPT && fn_data != NULL) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_ACCEPT && c->fn_data != NULL) {
     struct mg_tls_opts opts = {
 #ifdef TLS_TWOWAY
         .ca = mg_str(s_tls_ca),
@@ -89,7 +89,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/http-reverse-proxy/main.c b/examples/http-reverse-proxy/main.c
index 2d7d47c1..d61225d0 100644
--- a/examples/http-reverse-proxy/main.c
+++ b/examples/http-reverse-proxy/main.c
@@ -36,8 +36,8 @@ static void forward_request(struct mg_http_message *hm,
             (int) hm->uri.len, hm->uri.ptr));
 }
 
-static void fn2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_connection *c2 = (struct mg_connection *) fn_data;
+static void fn2(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_connection *c2 = (struct mg_connection *) c->fn_data;
   if (ev == MG_EV_READ) {
     // All incoming data from the backend, forward to the client
     if (c2 != NULL) mg_send(c2, c->recv.buf, c->recv.len);
@@ -48,8 +48,8 @@ static void fn2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   (void) ev_data;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_connection *c2 = fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_connection *c2 = c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     // Client request, create backend connection Note that we're passing
diff --git a/examples/http-server/main.c b/examples/http-server/main.c
index f2efbc5f..9e1e19ae 100644
--- a/examples/http-server/main.c
+++ b/examples/http-server/main.c
@@ -18,7 +18,7 @@ static void signal_handler(int signo) {
 
 // Event handler for the listening connection.
 // Simply serve static files from `s_root_dir`
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = ev_data, tmp = {0};
     struct mg_str unknown = mg_str_n("?", 1), *cl;
@@ -33,7 +33,6 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
              (int) hm->uri.len, hm->uri.ptr, (int) tmp.uri.len, tmp.uri.ptr,
              (int) cl->len, cl->ptr));
   }
-  (void) fn_data;
 }
 
 static void usage(const char *prog) {
diff --git a/examples/http-streaming-client/main.c b/examples/http-streaming-client/main.c
index 5c46a1a8..de4c9082 100644
--- a/examples/http-streaming-client/main.c
+++ b/examples/http-streaming-client/main.c
@@ -15,7 +15,7 @@
 static const char *s_url = "http://info.cern.ch";
 
 // Print HTTP response and signal that we're done
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_CONNECT) {
     // Connected to server. Extract host name from URL
     struct mg_str host = mg_url_host(s_url);
@@ -40,7 +40,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       data[1] += c->recv.len;
       fwrite(c->recv.buf, 1, c->recv.len, stdout);
       c->recv.len = 0;  // And cleanup the receive buffer. Streming!
-      if (data[1] >= data[0]) * (bool *) fn_data = true;
+      if (data[1] >= data[0]) * (bool *) c->fn_data = true;
     } else {
       struct mg_http_message hm;
       int n = mg_http_parse((char *) c->recv.buf, c->recv.len, &hm);
@@ -50,13 +50,13 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
         data[0] = n + hm.body.len;
         data[1] = c->recv.len;
         c->recv.len = 0;  // Cleanup receive buffer
-        if (data[1] >= data[0]) * (bool *) fn_data = true;
+        if (data[1] >= data[0]) * (bool *) c->fn_data = true;
       }
     }
   } else if (ev == MG_EV_CLOSE) {
-    *(bool *) fn_data = true;  // tell event loop to stop
+    *(bool *) c->fn_data = true;  // tell event loop to stop
   } else if (ev == MG_EV_ERROR) {
-    *(bool *) fn_data = true;  // Error, tell event loop to stop
+    *(bool *) c->fn_data = true;  // Error, tell event loop to stop
   }
   (void) ev_data;
 }
diff --git a/examples/huge-response/main.c b/examples/huge-response/main.c
index 209face5..3cc164fc 100644
--- a/examples/huge-response/main.c
+++ b/examples/huge-response/main.c
@@ -41,7 +41,7 @@ static size_t printdata(mg_pfn_t out, void *ptr, va_list *ap) {
   return n;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = ev_data;
     if (mg_http_match_uri(hm, "/api/data")) {
@@ -66,7 +66,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, hm, &opts);
     }
   }
-  (void) fn_data;
 }
 
 static void timer_fn(void *arg) {
diff --git a/examples/json-rpc-over-websocket/main.c b/examples/json-rpc-over-websocket/main.c
index 308aa397..2a4ce3aa 100644
--- a/examples/json-rpc-over-websocket/main.c
+++ b/examples/json-rpc-over-websocket/main.c
@@ -26,7 +26,7 @@ static void rpc_mul(struct mg_rpc_req *r) {
 // This RESTful server implements the following endpoints:
 //   /websocket - upgrade to Websocket, and implement websocket echo server
 //   any other URI serves static files from s_web_root
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_WS_OPEN) {
@@ -51,7 +51,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     if (io.buf) mg_ws_send(c, (char *) io.buf, io.len, WEBSOCKET_OP_TEXT);
     mg_iobuf_free(&io);
   }
-  (void) fn_data;
 }
 
 static void timer_fn(void *arg) {
diff --git a/examples/live-log/main.c b/examples/live-log/main.c
index b4b198b2..204e0c85 100644
--- a/examples/live-log/main.c
+++ b/examples/live-log/main.c
@@ -7,7 +7,7 @@
 //   /api/log/static - returns contents of log.txt file
 //   /api/log/live - hangs forever, and returns live log messages
 //   all other URI - serves web_root/ directory
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/log/static")) {
@@ -21,7 +21,6 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 static void log_message(const char *filename, const char *message) {
diff --git a/examples/microchip/same54-xpro/mqtt-client/main.c b/examples/microchip/same54-xpro/mqtt-client/main.c
index 0988574a..8656f4d4 100644
--- a/examples/microchip/same54-xpro/mqtt-client/main.c
+++ b/examples/microchip/same54-xpro/mqtt-client/main.c
@@ -31,7 +31,7 @@ void mg_random(void *buf, size_t len) {  // Use on-board RNG
   }
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     MG_INFO(("%lu CREATED", c->id));
     // c->is_hexdumping = 1;
@@ -66,7 +66,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     MG_INFO(("%lu CLOSED", c->id));
     s_conn = NULL;  // Mark that we're closed
   }
-  (void) fn_data;
 }
 
 // Timer function - recreate client connection if it is closed
diff --git a/examples/micropython/mongoose/main.c b/examples/micropython/mongoose/main.c
index c600b2ab..c3c413f4 100644
--- a/examples/micropython/mongoose/main.c
+++ b/examples/micropython/mongoose/main.c
@@ -8,9 +8,8 @@ static void t_fn(void *arg) {  // Tick periodically
   (void) arg;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) mg_http_reply(c, 200, "", "hi\n");
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/examples/mip-pcap/main.c b/examples/mip-pcap/main.c
index 81935ad4..87b5679b 100644
--- a/examples/mip-pcap/main.c
+++ b/examples/mip-pcap/main.c
@@ -42,20 +42,20 @@ static size_t pcap_rx(void *buf, size_t len, struct mg_tcpip_if *ifp) {
   return received;
 }
 
-static void fn2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn2(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     MG_DEBUG(("Got response (%d) %.*s...", (int) hm->message.len, 12,
               hm->message.ptr));
     c->is_draining = 1;
   } else if (ev == MG_EV_CONNECT) {
-    mg_printf(c, "GET %s HTTP/1.1\r\n\r\n", mg_url_uri((char *) fn_data));
+    mg_printf(c, "GET %s HTTP/1.1\r\n\r\n", mg_url_uri((char *) c->fn_data));
   } else if (ev == MG_EV_CLOSE) {
-    free(fn_data);
+    free(c->fn_data);
   }
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/debug")) {
@@ -75,7 +75,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
                     hm->message.ptr);
     }
   }
-  (void) ev_data, (void) fn_data;
+  (void) ev_data;
 }
 
 int main(int argc, char *argv[]) {
diff --git a/examples/modbus-dashboard/net.c b/examples/modbus-dashboard/net.c
index d261708f..aef60afd 100644
--- a/examples/modbus-dashboard/net.c
+++ b/examples/modbus-dashboard/net.c
@@ -40,7 +40,7 @@ uint64_t mg_now(void) {
 
 // SNTP connection event handler. When we get a response from an SNTP server,
 // adjust s_boot_timestamp. We'll get a valid time from that point on
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   uint64_t *expiration_time = (uint64_t *) c->data;
   if (ev == MG_EV_OPEN) {
     *expiration_time = mg_millis() + 3000;  // Store expiration time in 3s
@@ -51,7 +51,6 @@ static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_POLL) {
     if (mg_millis() > *expiration_time) c->is_closing = 1;
   }
-  (void) fn_data;
 }
 
 // SNTP timer function. Sync up time
@@ -99,7 +98,7 @@ static void handle_settings_get(struct mg_connection *c) {
 }
 
 // Modbus handler function
-static void mfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void mfn(struct mg_connection *c, int ev, void *ev_data) {
   struct conndata *cd = (struct conndata *) c->data;
   if (ev == MG_EV_READ) {
     MG_INFO(("%lu RECEIVED %lu", c->id, c->recv.len));
@@ -117,7 +116,7 @@ static void mfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       c->is_closing = 1;
     }
   }
-  (void) ev_data, (void) fn_data;
+  (void) ev_data;
 }
 
 static void send8(struct mg_connection *c, uint8_t val) {
@@ -242,10 +241,10 @@ static size_t print_mb_resp(void (*out)(char, void *), void *ptr, va_list *ap) {
 }
 
 // HTTP request handler function
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   struct conndata *cd = (struct conndata *) c->data;
   if (ev == MG_EV_ACCEPT) {
-    if (fn_data != NULL) {  // TLS listener!
+    if (c->fn_data != NULL) {  // TLS listener!
       struct mg_tls_opts opts = {0};
       opts.cert = mg_unpacked("/certs/server_cert.pem");
       opts.key = mg_unpacked("/certs/server_key.pem");
diff --git a/examples/modbus-dashboard/web_root/main.css b/examples/modbus-dashboard/web_root/main.css
index 8a757d00..f5b15ec3 100644
--- a/examples/modbus-dashboard/web_root/main.css
+++ b/examples/modbus-dashboard/web_root/main.css
@@ -1 +1 @@
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diff --git a/examples/mqtt-client-aws-iot/main.c b/examples/mqtt-client-aws-iot/main.c
index 808c6445..62f4b85c 100644
--- a/examples/mqtt-client-aws-iot/main.c
+++ b/examples/mqtt-client-aws-iot/main.c
@@ -38,7 +38,7 @@ static int s_qos = 1;
 
 #include "mongoose.h"
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_CONNECT) {
@@ -84,7 +84,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
 
   if (ev == MG_EV_ERROR || ev == MG_EV_CLOSE) {
     MG_INFO(("Got event %d, stopping...", ev));
-    *(bool *) fn_data = true;  // Signal that we're done
+    *(bool *) c->fn_data = true;  // Signal that we're done
   }
 }
 
diff --git a/examples/mqtt-client/main.c b/examples/mqtt-client/main.c
index c715de98..1012ca4f 100644
--- a/examples/mqtt-client/main.c
+++ b/examples/mqtt-client/main.c
@@ -24,7 +24,7 @@ static void signal_handler(int signo) {
   s_signo = signo;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     MG_INFO(("%lu CREATED", c->id));
     // c->is_hexdumping = 1;
@@ -65,7 +65,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     MG_INFO(("%lu CLOSED", c->id));
     s_conn = NULL;  // Mark that we're closed
   }
-  (void) fn_data;
 }
 
 // Timer function - recreate client connection if it is closed
diff --git a/examples/mqtt-dashboard/device/net.c b/examples/mqtt-dashboard/device/net.c
index f86bbcd9..2fec222b 100644
--- a/examples/mqtt-dashboard/device/net.c
+++ b/examples/mqtt-dashboard/device/net.c
@@ -190,7 +190,7 @@ static void rpc_ota_upload(struct mg_rpc_req *r) {
   }
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     MG_INFO(("%lu CREATED", c->id));
     // c->is_hexdumping = 1;
@@ -223,7 +223,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     MG_INFO(("%lu CLOSED", c->id));
     s_conn = NULL;  // Mark that we're closed
   }
-  (void) fn_data;
 }
 
 // Timer function - recreate client connection if it is closed
diff --git a/examples/mqtt-over-ws-client/main.c b/examples/mqtt-over-ws-client/main.c
index c9d0008b..74d2633b 100644
--- a/examples/mqtt-over-ws-client/main.c
+++ b/examples/mqtt-over-ws-client/main.c
@@ -20,7 +20,7 @@ static const char *s_url =
 
 static const char *s_topic = "mg/test";
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ERROR) {
     // On error, log error message
     MG_ERROR(("%p %s", c->fd, (char *) ev_data));
@@ -89,7 +89,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   }
 
   if (ev == MG_EV_ERROR || ev == MG_EV_CLOSE) {
-    *(bool *) fn_data = true;  // Signal that we're done
+    *(bool *) c->fn_data = true;  // Signal that we're done
   }
 }
 
diff --git a/examples/mqtt-server/main.c b/examples/mqtt-server/main.c
index 0b96ece4..77835e5f 100644
--- a/examples/mqtt-server/main.c
+++ b/examples/mqtt-server/main.c
@@ -53,7 +53,7 @@ size_t mg_mqtt_next_unsub(struct mg_mqtt_message *msg, struct mg_str *topic,
 }
 
 // Event handler function
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_MQTT_CMD) {
     struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
     MG_DEBUG(("cmd %d qos %d", mm->cmd, mm->qos));
@@ -131,7 +131,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       LIST_DELETE(struct sub, &s_subs, sub);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/multi-threaded-12m/main.c b/examples/multi-threaded-12m/main.c
index 64f49c1f..63bdcf52 100644
--- a/examples/multi-threaded-12m/main.c
+++ b/examples/multi-threaded-12m/main.c
@@ -43,7 +43,7 @@ static void *thread_function(void *param) {
 }
 
 // HTTP request callback
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN && c->is_listening) {
     // Start worker thread
     struct thread_data *data = calloc(1, sizeof(*data));  // Worker owns it
@@ -75,7 +75,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
         mg_ws_send(wc, data->ptr, data->len, WEBSOCKET_OP_TEXT);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/multi-threaded/main.c b/examples/multi-threaded/main.c
index 83ba42d0..b220cfa5 100644
--- a/examples/multi-threaded/main.c
+++ b/examples/multi-threaded/main.c
@@ -39,7 +39,7 @@ static void *thread_function(void *param) {
 }
 
 // HTTP request callback
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/fast")) {
@@ -58,7 +58,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     struct mg_str *data = (struct mg_str *) ev_data;
     mg_http_reply(c, 200, "", "Result: %.*s\n", data->len, data->ptr);
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/nxp/rt1020-evk-make-baremetal-builtin/main.c b/examples/nxp/rt1020-evk-make-baremetal-builtin/main.c
index e41e5cd0..e44b248c 100644
--- a/examples/nxp/rt1020-evk-make-baremetal-builtin/main.c
+++ b/examples/nxp/rt1020-evk-make-baremetal-builtin/main.c
@@ -32,8 +32,8 @@ static void timer_fn(void *arg) {
 }
 
 #ifndef RUNINFLASH
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/hello")) {  // Request to /api/hello
diff --git a/examples/nxp/rt1020-evk-make-freertos-builtin/main.c b/examples/nxp/rt1020-evk-make-freertos-builtin/main.c
index 0cf3bd02..ea7bd3a3 100644
--- a/examples/nxp/rt1020-evk-make-freertos-builtin/main.c
+++ b/examples/nxp/rt1020-evk-make-freertos-builtin/main.c
@@ -21,8 +21,8 @@ static void timer_fn(void *arg) {
            ifp->ndrop, ifp->nerr));
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/hello")) {  // Request to /api/hello
diff --git a/examples/rp2040/pico-rmii/main.c b/examples/rp2040/pico-rmii/main.c
index 3c2ed5a3..f41eb814 100644
--- a/examples/rp2040/pico-rmii/main.c
+++ b/examples/rp2040/pico-rmii/main.c
@@ -10,7 +10,7 @@
 
 #define CLKREFPIN 20  // either 20 or 22
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     mg_http_reply(c, 200, "", "ok\n");
   }
diff --git a/examples/smtp-client/main.c b/examples/smtp-client/main.c
index fa7e7354..4c2f34ac 100644
--- a/examples/smtp-client/main.c
+++ b/examples/smtp-client/main.c
@@ -13,7 +13,7 @@ static bool s_quit;
 
 enum { EHLO, STARTTLS, STARTTLS_WAIT, AUTH, FROM, TO, DATA, BODY, QUIT, END };
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   uint8_t *state = (uint8_t *) c->data;
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
@@ -69,7 +69,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     MG_INFO(("TLS handshake done! Sending EHLO again"));
     mg_printf(c, "EHLO myname\r\n");
   }
-  (void) fn_data, (void) ev_data;
+  (void) ev_data;
 }
 
 int main(void) {
diff --git a/examples/sntp-time-sync/main.c b/examples/sntp-time-sync/main.c
index 8e89e8d2..27801ac0 100644
--- a/examples/sntp-time-sync/main.c
+++ b/examples/sntp-time-sync/main.c
@@ -23,7 +23,7 @@ time_t my_time(time_t *tp) {
 }
 
 // SNTP client callback
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
     int64_t t = *(int64_t *) ev_data;
     MG_INFO(("Got SNTP time: %lld ms from epoch", t));
@@ -31,7 +31,7 @@ static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_CLOSE) {
     s_sntp_conn = NULL;
   }
-  (void) fn_data, (void) c;
+  (void) c;
 }
 
 // Called every 5 seconds. Increase that for production case.
diff --git a/examples/socks5-server/main.c b/examples/socks5-server/main.c
index bcdc862d..f673147a 100644
--- a/examples/socks5-server/main.c
+++ b/examples/socks5-server/main.c
@@ -79,14 +79,13 @@ static void exchange(struct mg_connection *c) {
   }
 }
 
-static void fn2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn2(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     exchange(c);
   } else if (ev == MG_EV_CLOSE) {
     disband(c);
   }
   (void) ev_data;
-  (void) fn_data;
 }
 
 //  Request, https://www.ietf.org/rfc/rfc1928.txt paragraph 4
@@ -149,7 +148,7 @@ static void request(struct mg_connection *c) {
   c->data[0] = STATE_ESTABLISHED;   // Mark ourselves as connected
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     // We use the first label byte as a state
     if (c->data[0] == STATE_HANDSHAKE) handshake(c);
@@ -158,7 +157,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_CLOSE) {
     disband(c);
   }
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/examples/stm32/nucleo-f429zi-make-baremetal-builtin-rndis/main.c b/examples/stm32/nucleo-f429zi-make-baremetal-builtin-rndis/main.c
index 228c90e3..dce94871 100644
--- a/examples/stm32/nucleo-f429zi-make-baremetal-builtin-rndis/main.c
+++ b/examples/stm32/nucleo-f429zi-make-baremetal-builtin-rndis/main.c
@@ -63,7 +63,7 @@ static bool usb_up(struct mg_tcpip_if *ifp) {
   return tud_inited() && tud_ready() && tud_connected();
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/debug")) {
@@ -74,7 +74,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_reply(c, 200, "", "hi\n");
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/stm32/nucleo-f746zg-make-baremetal-builtin-rndis/main.c b/examples/stm32/nucleo-f746zg-make-baremetal-builtin-rndis/main.c
index 228c90e3..dce94871 100644
--- a/examples/stm32/nucleo-f746zg-make-baremetal-builtin-rndis/main.c
+++ b/examples/stm32/nucleo-f746zg-make-baremetal-builtin-rndis/main.c
@@ -63,7 +63,7 @@ static bool usb_up(struct mg_tcpip_if *ifp) {
   return tud_inited() && tud_ready() && tud_connected();
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/debug")) {
@@ -74,7 +74,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_reply(c, 200, "", "hi\n");
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/stm32/nucleo-g031-make-baremetal-builtin/main.c b/examples/stm32/nucleo-g031-make-baremetal-builtin/main.c
index 4a0292b9..7a4be44c 100644
--- a/examples/stm32/nucleo-g031-make-baremetal-builtin/main.c
+++ b/examples/stm32/nucleo-g031-make-baremetal-builtin/main.c
@@ -42,8 +42,8 @@ static void timer_fn(void *arg) {
            ifp->nerr));
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_tcpip_if *ifp = (struct mg_tcpip_if *) c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/hello")) {  // Request to /api/hello
diff --git a/examples/tcp/main.c b/examples/tcp/main.c
index e5175288..58938f64 100644
--- a/examples/tcp/main.c
+++ b/examples/tcp/main.c
@@ -13,8 +13,8 @@ static struct c_res_s {
 } c_res;
 
 // CLIENT event handler
-static void cfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  int *i = &((struct c_res_s *) fn_data)->i;
+static void cfn(struct mg_connection *c, int ev, void *ev_data) {
+  int *i = &((struct c_res_s *) c->fn_data)->i;
   if (ev == MG_EV_OPEN) {
     MG_INFO(("CLIENT has been initialized"));
   } else if (ev == MG_EV_CONNECT) {
@@ -33,7 +33,7 @@ static void cfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_CLOSE) {
     MG_INFO(("CLIENT disconnected"));
     // signal we are done
-    ((struct c_res_s *) fn_data)->c = NULL;
+    ((struct c_res_s *) c->fn_data)->c = NULL;
   } else if (ev == MG_EV_ERROR) {
     MG_INFO(("CLIENT error: %s", (char *) ev_data));
   } else if (ev == MG_EV_POLL && *i != 0) {
@@ -51,7 +51,7 @@ static void cfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
 }
 
 // SERVER event handler
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN && c->is_listening == 1) {
     MG_INFO(("SERVER is listening"));
   } else if (ev == MG_EV_ACCEPT) {
@@ -72,7 +72,6 @@ static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_ERROR) {
     MG_INFO(("SERVER error: %s", (char *) ev_data));
   }
-  (void) fn_data;
 }
 
 // Timer function - recreate client connection if it is closed
diff --git a/examples/ti/ek-tm4c1294xl-make-baremetal-builtin-rndis/main.c b/examples/ti/ek-tm4c1294xl-make-baremetal-builtin-rndis/main.c
index c8ce33e3..750f4831 100644
--- a/examples/ti/ek-tm4c1294xl-make-baremetal-builtin-rndis/main.c
+++ b/examples/ti/ek-tm4c1294xl-make-baremetal-builtin-rndis/main.c
@@ -61,7 +61,7 @@ static bool usb_up(struct mg_tcpip_if *ifp) {
   return tud_inited() && tud_ready() && tud_connected();
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/debug")) {
@@ -72,7 +72,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_reply(c, 200, "", "hi\n");
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/timers/main.c b/examples/timers/main.c
index 53f2acaa..656427ea 100644
--- a/examples/timers/main.c
+++ b/examples/timers/main.c
@@ -11,7 +11,7 @@ static const char *s_listen_on = "http://localhost:8000";
 static const char *s_web_root = "web_root";
 
 // This RESTful server implements the following endpoints:
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/websocket")) {
@@ -28,7 +28,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     mg_ws_send(c, wm->data.ptr, wm->data.len, WEBSOCKET_OP_TEXT);
     mg_iobuf_del(&c->recv, 0, c->recv.len);
   }
-  (void) fn_data;
 }
 
 static void timer_fn(void *arg) {
diff --git a/examples/uart-bridge/main.c b/examples/uart-bridge/main.c
index 378087d4..fa45c54a 100644
--- a/examples/uart-bridge/main.c
+++ b/examples/uart-bridge/main.c
@@ -4,7 +4,7 @@
 #include "mongoose.h"
 const char *s_listening_url = "http://0.0.0.0:8000";
 
-void uart_bridge_fn(struct mg_connection *, int, void *, void *);
+void uart_bridge_fn(struct mg_connection *, int, void *);
 
 int main(void) {
   struct mg_mgr mgr;
diff --git a/examples/uart-bridge/net.c b/examples/uart-bridge/net.c
index 91b7aecc..4984d8a9 100644
--- a/examples/uart-bridge/net.c
+++ b/examples/uart-bridge/net.c
@@ -64,24 +64,23 @@ void config_write(struct mg_str config) {
 #endif
 
 // Event handler for a connected Websocket client
-static void ws_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void ws_fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
-    mg_ws_upgrade(c, evd, NULL);
+    mg_ws_upgrade(c, ev_data, NULL);
   } else if (ev == MG_EV_WS_OPEN) {
     // c->is_hexdumping = 1;
     c->data[0] = 'W';  // When WS handhake is done, mark us as WS client
   } else if (ev == MG_EV_WS_MSG) {
-    struct mg_ws_message *wm = (struct mg_ws_message *) evd;
+    struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
     uart_write(wm->data.ptr, wm->data.len);  // Send to UART
     c->recv.len = 0;                         // Discard received data
   } else if (ev == MG_EV_CLOSE) {
     if (c->is_listening) s_state.websocket.c = NULL;
   }
-  (void) fnd;
 }
 
 // Event handler for a connected TCP client
-static void tcp_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void tcp_fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ACCEPT) {
     // c->is_hexdumping = 1;
     c->data[0] = 'T';  // When client is connected, mark us as TCP client
@@ -91,7 +90,7 @@ static void tcp_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
   } else if (ev == MG_EV_CLOSE) {
     if (c->is_listening) s_state.tcp.c = NULL;
   }
-  (void) fnd, (void) evd;
+  (void) ev_data;
 }
 
 // Extract topic name from the MQTT address
@@ -102,7 +101,7 @@ static struct mg_str mqtt_topic(const char *name, const char *dflt) {
 }
 
 // Event handler for MQTT connection
-static void mq_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void mq_fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_MQTT_OPEN) {
@@ -113,12 +112,11 @@ static void mq_fn(struct mg_connection *c, int ev, void *evd, void *fnd) {
     sub_opts.qos = 1;
     mg_mqtt_sub(c, &sub_opts);  // Subscribe to RX topic
   } else if (ev == MG_EV_MQTT_MSG) {
-    struct mg_mqtt_message *mm = evd;        // MQTT message
+    struct mg_mqtt_message *mm = ev_data;    // MQTT message
     uart_write(mm->data.ptr, mm->data.len);  // Send to UART
   } else if (ev == MG_EV_CLOSE) {
     s_state.mqtt.c = NULL;
   }
-  (void) fnd, (void) evd;
 }
 
 // Software timer with a frequency close to the scheduling time slot
diff --git a/examples/udp-ssdp-search/main.c b/examples/udp-ssdp-search/main.c
index 4315ddab..70e0c293 100644
--- a/examples/udp-ssdp-search/main.c
+++ b/examples/udp-ssdp-search/main.c
@@ -5,8 +5,8 @@
 
 static const char *s_ssdp_url = "udp://239.255.255.250:1900";
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  MG_DEBUG(("%p got event: %d %p %p", c, ev, ev_data, fn_data));
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  MG_DEBUG(("%p got event: %d %p", c, ev, ev_data));
   if (ev == MG_EV_OPEN) {
     //    c->is_hexdumping = 1;
   } else if (ev == MG_EV_RESOLVE) {
diff --git a/examples/video-stream/main.c b/examples/video-stream/main.c
index 441386c9..5bd731d5 100644
--- a/examples/video-stream/main.c
+++ b/examples/video-stream/main.c
@@ -6,7 +6,7 @@
 // HTTP request handler function. It implements the following endpoints:
 //   /api/video1 - hangs forever, returns MJPEG video stream
 //   all other URI - serves web_root/ directory
-static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/video1")) {
@@ -22,7 +22,6 @@ static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 // The image stream is simulated by sending MJPEG frames specified by the
diff --git a/examples/wch/ch32v307-make-baremetal-builtin/main.c b/examples/wch/ch32v307-make-baremetal-builtin/main.c
index 981634c5..571744b3 100644
--- a/examples/wch/ch32v307-make-baremetal-builtin/main.c
+++ b/examples/wch/ch32v307-make-baremetal-builtin/main.c
@@ -59,7 +59,7 @@ void SysTick_Init(void) {
 }
 
 // https://mongoose.ws/documentation/#2-minute-integration-guide
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     mg_http_reply(c, 200, "", "ok %p %p\r\n", hm, fn_data);
diff --git a/examples/websocket-client/main.c b/examples/websocket-client/main.c
index bc21ea7c..6ef87067 100644
--- a/examples/websocket-client/main.c
+++ b/examples/websocket-client/main.c
@@ -10,7 +10,7 @@
 static const char *s_url = "ws://localhost:8000/websocket";
 
 // Print websocket response and signal that we're done
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     c->is_hexdumping = 1;
   } else if (ev == MG_EV_ERROR) {
@@ -26,7 +26,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   }
 
   if (ev == MG_EV_ERROR || ev == MG_EV_CLOSE || ev == MG_EV_WS_MSG) {
-    *(bool *) fn_data = true;  // Signal that we're done
+    *(bool *) c->fn_data = true;  // Signal that we're done
   }
 }
 
diff --git a/examples/websocket-server/main.c b/examples/websocket-server/main.c
index cacd2662..3c96c488 100644
--- a/examples/websocket-server/main.c
+++ b/examples/websocket-server/main.c
@@ -12,7 +12,7 @@ static const char *s_web_root = ".";
 //   /websocket - upgrade to Websocket, and implement websocket echo server
 //   /rest - respond with JSON string {"result": 123}
 //   any other URI serves static files from s_web_root
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_HTTP_MSG) {
@@ -34,7 +34,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
     mg_ws_send(c, wm->data.ptr, wm->data.len, WEBSOCKET_OP_TEXT);
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/webui-login/main.c b/examples/webui-login/main.c
index 99d50a30..0704fb70 100644
--- a/examples/webui-login/main.c
+++ b/examples/webui-login/main.c
@@ -43,7 +43,7 @@ static struct user *getuser(struct mg_http_message *hm) {
   return NULL;
 }
 
-void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct user *u = getuser(hm);
@@ -63,7 +63,6 @@ void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/webui-plain/main.c b/examples/webui-plain/main.c
index 96825ad9..c126798e 100644
--- a/examples/webui-plain/main.c
+++ b/examples/webui-plain/main.c
@@ -29,7 +29,7 @@ static void update_config(struct mg_str json, const char *path, char **value) {
   }
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN && c->is_listening) {
     s_config.url = strdup(MQTT_SERVER);
     s_config.pub = strdup(MQTT_PUBLISH_TOPIC);
@@ -52,7 +52,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/webui-push-rest/main.c b/examples/webui-push-rest/main.c
index 5c67a2ce..0ef3b731 100644
--- a/examples/webui-push-rest/main.c
+++ b/examples/webui-push-rest/main.c
@@ -37,7 +37,7 @@ static size_t printdata(mg_pfn_t out, void *ptr, va_list *ap) {
   (void) ap;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = ev_data;
     if (mg_http_match_uri(hm, "/api/data")) {
@@ -58,7 +58,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, hm, &opts);
     }
   }
-  (void) fn_data;
 }
 
 static void timer_fn(void *arg) {
diff --git a/examples/webui-push-ws/main.c b/examples/webui-push-ws/main.c
index cf6226df..f66fdcdb 100644
--- a/examples/webui-push-ws/main.c
+++ b/examples/webui-push-ws/main.c
@@ -10,7 +10,7 @@
 static const char *s_listen_on = "http://localhost:8000";
 static const char *s_web_root = "web_root";
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/watch")) {
@@ -21,7 +21,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 // Push to all watchers
diff --git a/examples/webui-rest/main.c b/examples/webui-rest/main.c
index 155bcf9c..43177703 100644
--- a/examples/webui-rest/main.c
+++ b/examples/webui-rest/main.c
@@ -13,7 +13,7 @@
 static const char *s_http_addr = "http://localhost:8000";  // HTTP port
 static const char *s_root_dir = "web_root";
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/f1")) {
@@ -34,7 +34,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, hm, &opts);
     }
   }
-  (void) fn_data;
 }
 
 int main(void) {
diff --git a/examples/wifi-router-dashboard/net.c b/examples/wifi-router-dashboard/net.c
index d88a574d..7591fcae 100644
--- a/examples/wifi-router-dashboard/net.c
+++ b/examples/wifi-router-dashboard/net.c
@@ -109,7 +109,7 @@ static int event_next(int no, struct event *e) {
 
 // SNTP connection event handler. When we get a response from an SNTP server,
 // adjust s_boot_timestamp. We'll get a valid time from that point on
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   uint64_t *expiration_time = (uint64_t *) c->data;
   if (ev == MG_EV_OPEN) {
     *expiration_time = mg_millis() + 3000;  // Store expiration time in 3s
@@ -120,7 +120,6 @@ static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_POLL) {
     if (mg_millis() > *expiration_time) c->is_closing = 1;
   }
-  (void) fn_data;
 }
 
 static void timer_sntp_fn(void *param) {  // SNTP timer function. Sync up time
@@ -271,9 +270,9 @@ static void handle_dhcp_get(struct mg_connection *c) {
 }
 
 // HTTP request handler function
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ACCEPT) {
-    if (fn_data != NULL) {  // TLS
+    if (c->fn_data != NULL) {  // TLS
       struct mg_tls_opts opts = {0};
       opts.cert = mg_str(s_tls_cert);
       opts.key = mg_str(s_tls_key);
@@ -316,7 +315,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
               hm->method.ptr, (int) hm->uri.len, hm->uri.ptr, (int) 3,
               &c->send.buf[9]));
   }
-  (void) fn_data;
 }
 
 void web_init(struct mg_mgr *mgr) {
diff --git a/examples/zephyr/http-client/src/main.c b/examples/zephyr/http-client/src/main.c
index 9f786aac..a2c77df5 100644
--- a/examples/zephyr/http-client/src/main.c
+++ b/examples/zephyr/http-client/src/main.c
@@ -14,7 +14,7 @@ static int s_connected = 0;
 static bool done = false;
 
 // Print HTTP response and signal that we're done
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // Connection created. Store connect expiration time in c->data
     *(int64_t *) c->data = mg_millis() + s_timeout_ms;
@@ -49,9 +49,9 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     MG_INFO(("%.*s", (int) hm->message.len, hm->message.ptr));
     c->is_draining = 1;        // Tell mongoose to close this connection
-    *(bool *) fn_data = true;  // Tell event loop to stop
+    *(bool *) c->fn_data = true;  // Tell event loop to stop
   } else if (ev == MG_EV_ERROR) {
-    *(bool *) fn_data = true;  // Error, tell event loop to stop
+    *(bool *) c->fn_data = true;  // Error, tell event loop to stop
   }
 }
 
@@ -63,7 +63,7 @@ time_t ourtime(time_t *tp) {
 }
 
 // SNTP callback. Modifies s_boot_timestamp, to make ourtime() correct
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
     int64_t t = *(int64_t *) ev_data;
     MG_INFO(("Got SNTP time: %lld ms from epoch", t));
diff --git a/examples/zephyr/http-server/src/main.c b/examples/zephyr/http-server/src/main.c
index 6f250f5a..b306fdb0 100644
--- a/examples/zephyr/http-server/src/main.c
+++ b/examples/zephyr/http-server/src/main.c
@@ -11,8 +11,8 @@ static time_t s_boot_timestamp = 0;
 static struct mg_connection *s_sntp_conn = NULL;
 
 // Event handler for the listening HTTP/HTTPS connection.
-static void wcb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  if (ev == MG_EV_ACCEPT && fn_data != NULL) {
+static void wcb(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_ACCEPT && c->fn_data != NULL) {
     struct mg_tls_opts opts = {.cert = s_ssl_cert, .key = s_ssl_key};
     mg_tls_init(c, &opts);
   } else if (ev == MG_EV_HTTP_MSG) {
@@ -49,7 +49,7 @@ time_t ourtime(time_t *tp) {
 }
 
 // SNTP callback. Modifies s_boot_timestamp, to make ourtime() correct
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
     int64_t t = *(int64_t *) ev_data;
     MG_INFO(("Got SNTP time: %lld ms from epoch", t));
diff --git a/examples/zephyr/mqtt-aws-client/src/main.c b/examples/zephyr/mqtt-aws-client/src/main.c
index 606b433f..2d88bdeb 100644
--- a/examples/zephyr/mqtt-aws-client/src/main.c
+++ b/examples/zephyr/mqtt-aws-client/src/main.c
@@ -16,7 +16,7 @@ static const char *s_tx_topic = "d/tx";
 static int s_qos = 1;
 static int s_connected = 0;
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_ERROR) {
@@ -67,7 +67,7 @@ time_t ourtime(time_t *tp) {
 }
 
 // SNTP callback. Modifies s_boot_timestamp, to make ourtime() correct
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
     int64_t t = *(int64_t *) ev_data;
     MG_INFO(("Got SNTP time: %lld ms from epoch", t));
diff --git a/examples/zephyr/websocket-server/src/main.c b/examples/zephyr/websocket-server/src/main.c
index ee9aa69c..ecf5d0e9 100644
--- a/examples/zephyr/websocket-server/src/main.c
+++ b/examples/zephyr/websocket-server/src/main.c
@@ -13,10 +13,10 @@ static struct mg_connection *s_sntp_conn = NULL;
 // This RESTful server implements the following endpoints:
 //   /websocket - upgrade to Websocket, and implement websocket echo server
 //   /api/rest - respond with JSON string {"result": 123}
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_OPEN) {
     c->is_hexdumping = 1;
-  } else if (ev == MG_EV_ACCEPT && fn_data != NULL) {
+  } else if (ev == MG_EV_ACCEPT && c->fn_data != NULL) {
     struct mg_tls_opts opts = {.cert = s_ssl_cert, .key = s_ssl_key};
     mg_tls_init(c, &opts);
   } else if (ev == MG_EV_HTTP_MSG) {
@@ -35,7 +35,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     MG_INFO(("Got wm: %p, data: %p, %d = %*.s", wm, wm->data.ptr, wm->data.len, wm->data.len, wm->data.ptr));
     mg_ws_send(c, wm->data.ptr, wm->data.len, WEBSOCKET_OP_TEXT);
   }
-  (void) fn_data;
 }
 
 // example system time()-like function
@@ -46,7 +45,7 @@ time_t ourtime(time_t *tp) {
 }
 
 // SNTP callback. Modifies s_boot_timestamp, to make ourtime() correct
-static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
     int64_t t = *(int64_t *) ev_data;
     MG_INFO(("Got SNTP time: %lld ms from epoch", t));
diff --git a/mongoose.c b/mongoose.c
index b892772c..b3d8d1cd 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -852,8 +852,7 @@ bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
   return true;
 }
 
-static void dns_cb(struct mg_connection *c, int ev, void *ev_data,
-                   void *fn_data) {
+static void dns_cb(struct mg_connection *c, int ev, void *ev_data) {
   struct dns_data *d, *tmp;
   struct dns_data **head = (struct dns_data **) &c->mgr->active_dns_requests;
   if (ev == MG_EV_POLL) {
@@ -907,7 +906,6 @@ static void dns_cb(struct mg_connection *c, int ev, void *ev_data,
       mg_dns_free(head, d);
     }
   }
-  (void) fn_data;
 }
 
 static bool mg_dns_send(struct mg_connection *c, const struct mg_str *name,
@@ -1006,8 +1004,8 @@ void mg_call(struct mg_connection *c, int ev, void *ev_data) {
   // Run user-defined handler first, in order to give it an ability
   // to intercept processing (e.g. clean input buffer) before the
   // protocol handler kicks in
-  if (c->fn != NULL) c->fn(c, ev, ev_data, c->fn_data);
-  if (c->pfn != NULL) c->pfn(c, ev, ev_data, c->pfn_data);
+  if (c->fn != NULL) c->fn(c, ev, ev_data);
+  if (c->pfn != NULL) c->pfn(c, ev, ev_data);
 }
 
 void mg_error(struct mg_connection *c, const char *fmt, ...) {
@@ -1018,7 +1016,7 @@ void mg_error(struct mg_connection *c, const char *fmt, ...) {
   va_end(ap);
   MG_ERROR(("%lu %ld %s", c->id, c->fd, buf));
   c->is_closing = 1;             // Set is_closing before sending MG_EV_CALL
-  mg_call(c, MG_EV_ERROR, buf);  // Let user handler to override it
+  mg_call(c, MG_EV_ERROR, buf);  // Let user handler override it
 }
 
 #ifdef MG_ENABLE_LINES
@@ -2286,7 +2284,7 @@ void mg_http_reply(struct mg_connection *c, int code, const char *headers,
   c->is_resp = 0;
 }
 
-static void http_cb(struct mg_connection *, int, void *, void *);
+static void http_cb(struct mg_connection *, int, void *);
 static void restore_http_cb(struct mg_connection *c) {
   mg_fs_close((struct mg_fd *) c->pfn_data);
   c->pfn_data = NULL;
@@ -2300,10 +2298,9 @@ char *mg_http_etag(char *buf, size_t len, size_t size, time_t mtime) {
   return buf;
 }
 
-static void static_cb(struct mg_connection *c, int ev, void *ev_data,
-                      void *fn_data) {
+static void static_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_WRITE || ev == MG_EV_POLL) {
-    struct mg_fd *fd = (struct mg_fd *) fn_data;
+    struct mg_fd *fd = (struct mg_fd *) c->pfn_data;
     // Read to send IO buffer directly, avoid extra on-stack buffer
     size_t n, max = MG_IO_SIZE, space;
     size_t *cl = (size_t *) &c->data[(sizeof(c->data) - sizeof(size_t)) /
@@ -2828,7 +2825,7 @@ static int skip_chunk(const char *buf, int len, int *pl, int *dl) {
   return i + 2 + n + 2;
 }
 
-static void http_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void http_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ || ev == MG_EV_CLOSE) {
     struct mg_http_message hm;
     size_t ofs = 0;  // Parsing offset
@@ -2890,10 +2887,10 @@ static void http_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
     }
     if (ofs > 0) mg_iobuf_del(&c->recv, 0, ofs);  // Delete processed data
   }
-  (void) evd, (void) fnd;
+  (void) ev_data;
 }
 
-static void mg_hfn(struct mg_connection *c, int ev, void *ev_data, void *fnd) {
+static void mg_hfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/quit")) {
@@ -2908,7 +2905,7 @@ static void mg_hfn(struct mg_connection *c, int ev, void *ev_data, void *fnd) {
       mg_http_reply(c, 200, "", "hi\n");
     }
   } else if (ev == MG_EV_CLOSE) {
-    if (c->data[0] == 'X') *(bool *) fnd = true;
+    if (c->data[0] == 'X') *(bool *) c->fn_data = true;
   }
 }
 
@@ -4062,7 +4059,8 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
       }
       if (p > end) return MQTT_MALFORMED;
       if (version == 5 && p + 2 < end) {
-        len_len = (uint32_t) decode_varint(p, (size_t) (end - p), &m->props_size);
+        len_len =
+            (uint32_t) decode_varint(p, (size_t) (end - p), &m->props_size);
         if (!len_len) return MQTT_MALFORMED;
         m->props_start = (size_t) (p + len_len - buf);
         p += len_len + m->props_size;
@@ -4078,8 +4076,7 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
   return MQTT_OK;
 }
 
-static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data,
-                    void *fn_data) {
+static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     for (;;) {
       uint8_t version = c->is_mqtt5 ? 5 : 4;
@@ -4147,7 +4144,6 @@ static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data,
     }
   }
   (void) ev_data;
-  (void) fn_data;
 }
 
 void mg_mqtt_ping(struct mg_connection *nc) {
@@ -4191,289 +4187,6 @@ struct mg_connection *mg_mqtt_listen(struct mg_mgr *mgr, const char *url,
   return c;
 }
 
-#ifdef MG_ENABLE_LINES
-#line 1 "src/net.c"
-#endif
-
-
-
-
-
-
-
-
-
-size_t mg_vprintf(struct mg_connection *c, const char *fmt, va_list *ap) {
-  size_t old = c->send.len;
-  mg_vxprintf(mg_pfn_iobuf, &c->send, fmt, ap);
-  return c->send.len - old;
-}
-
-size_t mg_printf(struct mg_connection *c, const char *fmt, ...) {
-  size_t len = 0;
-  va_list ap;
-  va_start(ap, fmt);
-  len = mg_vprintf(c, fmt, &ap);
-  va_end(ap);
-  return len;
-}
-
-static bool mg_atonl(struct mg_str str, struct mg_addr *addr) {
-  uint32_t localhost = mg_htonl(0x7f000001);
-  if (mg_vcasecmp(&str, "localhost") != 0) return false;
-  memcpy(addr->ip, &localhost, sizeof(uint32_t));
-  addr->is_ip6 = false;
-  return true;
-}
-
-static bool mg_atone(struct mg_str str, struct mg_addr *addr) {
-  if (str.len > 0) return false;
-  memset(addr->ip, 0, sizeof(addr->ip));
-  addr->is_ip6 = false;
-  return true;
-}
-
-static bool mg_aton4(struct mg_str str, struct mg_addr *addr) {
-  uint8_t data[4] = {0, 0, 0, 0};
-  size_t i, num_dots = 0;
-  for (i = 0; i < str.len; i++) {
-    if (str.ptr[i] >= '0' && str.ptr[i] <= '9') {
-      int octet = data[num_dots] * 10 + (str.ptr[i] - '0');
-      if (octet > 255) return false;
-      data[num_dots] = (uint8_t) octet;
-    } else if (str.ptr[i] == '.') {
-      if (num_dots >= 3 || i == 0 || str.ptr[i - 1] == '.') return false;
-      num_dots++;
-    } else {
-      return false;
-    }
-  }
-  if (num_dots != 3 || str.ptr[i - 1] == '.') return false;
-  memcpy(&addr->ip, data, sizeof(data));
-  addr->is_ip6 = false;
-  return true;
-}
-
-static bool mg_v4mapped(struct mg_str str, struct mg_addr *addr) {
-  int i;
-  uint32_t ipv4;
-  if (str.len < 14) return false;
-  if (str.ptr[0] != ':' || str.ptr[1] != ':' || str.ptr[6] != ':') return false;
-  for (i = 2; i < 6; i++) {
-    if (str.ptr[i] != 'f' && str.ptr[i] != 'F') return false;
-  }
-  // struct mg_str s = mg_str_n(&str.ptr[7], str.len - 7);
-  if (!mg_aton4(mg_str_n(&str.ptr[7], str.len - 7), addr)) return false;
-  memcpy(&ipv4, addr->ip, sizeof(ipv4));
-  memset(addr->ip, 0, sizeof(addr->ip));
-  addr->ip[10] = addr->ip[11] = 255;
-  memcpy(&addr->ip[12], &ipv4, 4);
-  addr->is_ip6 = true;
-  return true;
-}
-
-static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
-  size_t i, j = 0, n = 0, dc = 42;
-  addr->scope_id = 0;
-  if (str.len > 2 && str.ptr[0] == '[') str.ptr++, str.len -= 2;
-  if (mg_v4mapped(str, addr)) return true;
-  for (i = 0; i < str.len; i++) {
-    if ((str.ptr[i] >= '0' && str.ptr[i] <= '9') ||
-        (str.ptr[i] >= 'a' && str.ptr[i] <= 'f') ||
-        (str.ptr[i] >= 'A' && str.ptr[i] <= 'F')) {
-      unsigned long val;
-      if (i > j + 3) return false;
-      // MG_DEBUG(("%lu %lu [%.*s]", i, j, (int) (i - j + 1), &str.ptr[j]));
-      val = mg_unhexn(&str.ptr[j], i - j + 1);
-      addr->ip[n] = (uint8_t) ((val >> 8) & 255);
-      addr->ip[n + 1] = (uint8_t) (val & 255);
-    } else if (str.ptr[i] == ':') {
-      j = i + 1;
-      if (i > 0 && str.ptr[i - 1] == ':') {
-        dc = n;  // Double colon
-        if (i > 1 && str.ptr[i - 2] == ':') return false;
-      } else if (i > 0) {
-        n += 2;
-      }
-      if (n > 14) return false;
-      addr->ip[n] = addr->ip[n + 1] = 0;  // For trailing ::
-    } else if (str.ptr[i] == '%') {       // Scope ID
-      for (i = i + 1; i < str.len; i++) {
-        if (str.ptr[i] < '0' || str.ptr[i] > '9') return false;
-        addr->scope_id = (uint8_t) (addr->scope_id * 10);
-        addr->scope_id = (uint8_t) (addr->scope_id + (str.ptr[i] - '0'));
-      }
-    } else {
-      return false;
-    }
-  }
-  if (n < 14 && dc == 42) return false;
-  if (n < 14) {
-    memmove(&addr->ip[dc + (14 - n)], &addr->ip[dc], n - dc + 2);
-    memset(&addr->ip[dc], 0, 14 - n);
-  }
-
-  addr->is_ip6 = true;
-  return true;
-}
-
-bool mg_aton(struct mg_str str, struct mg_addr *addr) {
-  // MG_INFO(("[%.*s]", (int) str.len, str.ptr));
-  return mg_atone(str, addr) || mg_atonl(str, addr) || mg_aton4(str, addr) ||
-         mg_aton6(str, addr);
-}
-
-struct mg_connection *mg_alloc_conn(struct mg_mgr *mgr) {
-  struct mg_connection *c =
-      (struct mg_connection *) calloc(1, sizeof(*c) + mgr->extraconnsize);
-  if (c != NULL) {
-    c->mgr = mgr;
-    c->send.align = c->recv.align = c->rtls.align = MG_IO_SIZE;
-    c->id = ++mgr->nextid;
-    MG_PROF_INIT(c);
-  }
-  return c;
-}
-
-void mg_close_conn(struct mg_connection *c) {
-  mg_resolve_cancel(c);  // Close any pending DNS query
-  LIST_DELETE(struct mg_connection, &c->mgr->conns, c);
-  if (c == c->mgr->dns4.c) c->mgr->dns4.c = NULL;
-  if (c == c->mgr->dns6.c) c->mgr->dns6.c = NULL;
-  // Order of operations is important. `MG_EV_CLOSE` event must be fired
-  // before we deallocate received data, see #1331
-  mg_call(c, MG_EV_CLOSE, NULL);
-  MG_DEBUG(("%lu %ld closed", c->id, c->fd));
-  MG_PROF_DUMP(c);
-  MG_PROF_FREE(c);
-
-  mg_tls_free(c);
-  mg_iobuf_free(&c->recv);
-  mg_iobuf_free(&c->send);
-  mg_iobuf_free(&c->rtls);
-  mg_bzero((unsigned char *) c, sizeof(*c));
-  free(c);
-}
-
-struct mg_connection *mg_connect(struct mg_mgr *mgr, const char *url,
-                                 mg_event_handler_t fn, void *fn_data) {
-  struct mg_connection *c = NULL;
-  if (url == NULL || url[0] == '\0') {
-    MG_ERROR(("null url"));
-  } else if ((c = mg_alloc_conn(mgr)) == NULL) {
-    MG_ERROR(("OOM"));
-  } else {
-    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
-    c->is_udp = (strncmp(url, "udp:", 4) == 0);
-    c->fd = (void *) (size_t) MG_INVALID_SOCKET;
-    c->fn = fn;
-    c->is_client = true;
-    c->fn_data = fn_data;
-    MG_DEBUG(("%lu %ld %s", c->id, c->fd, url));
-    mg_call(c, MG_EV_OPEN, (void *) url);
-    mg_resolve(c, url);
-  }
-  return c;
-}
-
-struct mg_connection *mg_listen(struct mg_mgr *mgr, const char *url,
-                                mg_event_handler_t fn, void *fn_data) {
-  struct mg_connection *c = NULL;
-  if ((c = mg_alloc_conn(mgr)) == NULL) {
-    MG_ERROR(("OOM %s", url));
-  } else if (!mg_open_listener(c, url)) {
-    MG_ERROR(("Failed: %s, errno %d", url, errno));
-    MG_PROF_FREE(c);
-    free(c);
-    c = NULL;
-  } else {
-    c->is_listening = 1;
-    c->is_udp = strncmp(url, "udp:", 4) == 0;
-    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
-    c->fn = fn;
-    c->fn_data = fn_data;
-    mg_call(c, MG_EV_OPEN, NULL);
-    if (mg_url_is_ssl(url)) c->is_tls = 1;  // Accepted connection must
-    MG_DEBUG(("%lu %ld %s", c->id, c->fd, url));
-  }
-  return c;
-}
-
-struct mg_connection *mg_wrapfd(struct mg_mgr *mgr, int fd,
-                                mg_event_handler_t fn, void *fn_data) {
-  struct mg_connection *c = mg_alloc_conn(mgr);
-  if (c != NULL) {
-    c->fd = (void *) (size_t) fd;
-    c->fn = fn;
-    c->fn_data = fn_data;
-    MG_EPOLL_ADD(c);
-    mg_call(c, MG_EV_OPEN, NULL);
-    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
-  }
-  return c;
-}
-
-struct mg_timer *mg_timer_add(struct mg_mgr *mgr, uint64_t milliseconds,
-                              unsigned flags, void (*fn)(void *), void *arg) {
-  struct mg_timer *t = (struct mg_timer *) calloc(1, sizeof(*t));
-  if (t != NULL) {
-    mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
-    t->id = mgr->timerid++;
-  }
-  return t;
-}
-
-long mg_io_recv(struct mg_connection *c, void *buf, size_t len) {
-  if (c->rtls.len == 0) return MG_IO_WAIT;
-  if (len > c->rtls.len) len = c->rtls.len;
-  memcpy(buf, c->rtls.buf, len);
-  mg_iobuf_del(&c->rtls, 0, len);
-  return (long) len;
-}
-
-void mg_mgr_free(struct mg_mgr *mgr) {
-  struct mg_connection *c;
-  struct mg_timer *tmp, *t = mgr->timers;
-  while (t != NULL) tmp = t->next, free(t), t = tmp;
-  mgr->timers = NULL;  // Important. Next call to poll won't touch timers
-  for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
-  mg_mgr_poll(mgr, 0);
-#if MG_ENABLE_FREERTOS_TCP
-  FreeRTOS_DeleteSocketSet(mgr->ss);
-#endif
-  MG_DEBUG(("All connections closed"));
-#if MG_ENABLE_EPOLL
-  if (mgr->epoll_fd >= 0) close(mgr->epoll_fd), mgr->epoll_fd = -1;
-#endif
-  mg_tls_ctx_free(mgr);
-}
-
-void mg_mgr_init(struct mg_mgr *mgr) {
-  memset(mgr, 0, sizeof(*mgr));
-#if MG_ENABLE_EPOLL
-  if ((mgr->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0)
-    MG_ERROR(("epoll_create1 errno %d", errno));
-#else
-  mgr->epoll_fd = -1;
-#endif
-#if MG_ARCH == MG_ARCH_WIN32 && MG_ENABLE_WINSOCK
-  // clang-format off
-  { WSADATA data; WSAStartup(MAKEWORD(2, 2), &data); }
-  // clang-format on
-#elif MG_ENABLE_FREERTOS_TCP
-  mgr->ss = FreeRTOS_CreateSocketSet();
-#elif defined(__unix) || defined(__unix__) || defined(__APPLE__)
-  // Ignore SIGPIPE signal, so if client cancels the request, it
-  // won't kill the whole process.
-  signal(SIGPIPE, SIG_IGN);
-#endif
-  mgr->pipe = MG_INVALID_SOCKET;
-  mgr->dnstimeout = 3000;
-  mgr->dns4.url = "udp://8.8.8.8:53";
-  mgr->dns6.url = "udp://[2001:4860:4860::8888]:53";
-  mg_tls_ctx_init(mgr);
-}
-
 #ifdef MG_ENABLE_LINES
 #line 1 "src/net_builtin.c"
 #endif
@@ -5583,6 +5296,289 @@ bool mg_send(struct mg_connection *c, const void *buf, size_t len) {
 }
 #endif  // MG_ENABLE_TCPIP
 
+#ifdef MG_ENABLE_LINES
+#line 1 "src/net.c"
+#endif
+
+
+
+
+
+
+
+
+
+size_t mg_vprintf(struct mg_connection *c, const char *fmt, va_list *ap) {
+  size_t old = c->send.len;
+  mg_vxprintf(mg_pfn_iobuf, &c->send, fmt, ap);
+  return c->send.len - old;
+}
+
+size_t mg_printf(struct mg_connection *c, const char *fmt, ...) {
+  size_t len = 0;
+  va_list ap;
+  va_start(ap, fmt);
+  len = mg_vprintf(c, fmt, &ap);
+  va_end(ap);
+  return len;
+}
+
+static bool mg_atonl(struct mg_str str, struct mg_addr *addr) {
+  uint32_t localhost = mg_htonl(0x7f000001);
+  if (mg_vcasecmp(&str, "localhost") != 0) return false;
+  memcpy(addr->ip, &localhost, sizeof(uint32_t));
+  addr->is_ip6 = false;
+  return true;
+}
+
+static bool mg_atone(struct mg_str str, struct mg_addr *addr) {
+  if (str.len > 0) return false;
+  memset(addr->ip, 0, sizeof(addr->ip));
+  addr->is_ip6 = false;
+  return true;
+}
+
+static bool mg_aton4(struct mg_str str, struct mg_addr *addr) {
+  uint8_t data[4] = {0, 0, 0, 0};
+  size_t i, num_dots = 0;
+  for (i = 0; i < str.len; i++) {
+    if (str.ptr[i] >= '0' && str.ptr[i] <= '9') {
+      int octet = data[num_dots] * 10 + (str.ptr[i] - '0');
+      if (octet > 255) return false;
+      data[num_dots] = (uint8_t) octet;
+    } else if (str.ptr[i] == '.') {
+      if (num_dots >= 3 || i == 0 || str.ptr[i - 1] == '.') return false;
+      num_dots++;
+    } else {
+      return false;
+    }
+  }
+  if (num_dots != 3 || str.ptr[i - 1] == '.') return false;
+  memcpy(&addr->ip, data, sizeof(data));
+  addr->is_ip6 = false;
+  return true;
+}
+
+static bool mg_v4mapped(struct mg_str str, struct mg_addr *addr) {
+  int i;
+  uint32_t ipv4;
+  if (str.len < 14) return false;
+  if (str.ptr[0] != ':' || str.ptr[1] != ':' || str.ptr[6] != ':') return false;
+  for (i = 2; i < 6; i++) {
+    if (str.ptr[i] != 'f' && str.ptr[i] != 'F') return false;
+  }
+  // struct mg_str s = mg_str_n(&str.ptr[7], str.len - 7);
+  if (!mg_aton4(mg_str_n(&str.ptr[7], str.len - 7), addr)) return false;
+  memcpy(&ipv4, addr->ip, sizeof(ipv4));
+  memset(addr->ip, 0, sizeof(addr->ip));
+  addr->ip[10] = addr->ip[11] = 255;
+  memcpy(&addr->ip[12], &ipv4, 4);
+  addr->is_ip6 = true;
+  return true;
+}
+
+static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
+  size_t i, j = 0, n = 0, dc = 42;
+  addr->scope_id = 0;
+  if (str.len > 2 && str.ptr[0] == '[') str.ptr++, str.len -= 2;
+  if (mg_v4mapped(str, addr)) return true;
+  for (i = 0; i < str.len; i++) {
+    if ((str.ptr[i] >= '0' && str.ptr[i] <= '9') ||
+        (str.ptr[i] >= 'a' && str.ptr[i] <= 'f') ||
+        (str.ptr[i] >= 'A' && str.ptr[i] <= 'F')) {
+      unsigned long val;
+      if (i > j + 3) return false;
+      // MG_DEBUG(("%lu %lu [%.*s]", i, j, (int) (i - j + 1), &str.ptr[j]));
+      val = mg_unhexn(&str.ptr[j], i - j + 1);
+      addr->ip[n] = (uint8_t) ((val >> 8) & 255);
+      addr->ip[n + 1] = (uint8_t) (val & 255);
+    } else if (str.ptr[i] == ':') {
+      j = i + 1;
+      if (i > 0 && str.ptr[i - 1] == ':') {
+        dc = n;  // Double colon
+        if (i > 1 && str.ptr[i - 2] == ':') return false;
+      } else if (i > 0) {
+        n += 2;
+      }
+      if (n > 14) return false;
+      addr->ip[n] = addr->ip[n + 1] = 0;  // For trailing ::
+    } else if (str.ptr[i] == '%') {       // Scope ID
+      for (i = i + 1; i < str.len; i++) {
+        if (str.ptr[i] < '0' || str.ptr[i] > '9') return false;
+        addr->scope_id = (uint8_t) (addr->scope_id * 10);
+        addr->scope_id = (uint8_t) (addr->scope_id + (str.ptr[i] - '0'));
+      }
+    } else {
+      return false;
+    }
+  }
+  if (n < 14 && dc == 42) return false;
+  if (n < 14) {
+    memmove(&addr->ip[dc + (14 - n)], &addr->ip[dc], n - dc + 2);
+    memset(&addr->ip[dc], 0, 14 - n);
+  }
+
+  addr->is_ip6 = true;
+  return true;
+}
+
+bool mg_aton(struct mg_str str, struct mg_addr *addr) {
+  // MG_INFO(("[%.*s]", (int) str.len, str.ptr));
+  return mg_atone(str, addr) || mg_atonl(str, addr) || mg_aton4(str, addr) ||
+         mg_aton6(str, addr);
+}
+
+struct mg_connection *mg_alloc_conn(struct mg_mgr *mgr) {
+  struct mg_connection *c =
+      (struct mg_connection *) calloc(1, sizeof(*c) + mgr->extraconnsize);
+  if (c != NULL) {
+    c->mgr = mgr;
+    c->send.align = c->recv.align = c->rtls.align = MG_IO_SIZE;
+    c->id = ++mgr->nextid;
+    MG_PROF_INIT(c);
+  }
+  return c;
+}
+
+void mg_close_conn(struct mg_connection *c) {
+  mg_resolve_cancel(c);  // Close any pending DNS query
+  LIST_DELETE(struct mg_connection, &c->mgr->conns, c);
+  if (c == c->mgr->dns4.c) c->mgr->dns4.c = NULL;
+  if (c == c->mgr->dns6.c) c->mgr->dns6.c = NULL;
+  // Order of operations is important. `MG_EV_CLOSE` event must be fired
+  // before we deallocate received data, see #1331
+  mg_call(c, MG_EV_CLOSE, NULL);
+  MG_DEBUG(("%lu %ld closed", c->id, c->fd));
+  MG_PROF_DUMP(c);
+  MG_PROF_FREE(c);
+
+  mg_tls_free(c);
+  mg_iobuf_free(&c->recv);
+  mg_iobuf_free(&c->send);
+  mg_iobuf_free(&c->rtls);
+  mg_bzero((unsigned char *) c, sizeof(*c));
+  free(c);
+}
+
+struct mg_connection *mg_connect(struct mg_mgr *mgr, const char *url,
+                                 mg_event_handler_t fn, void *fn_data) {
+  struct mg_connection *c = NULL;
+  if (url == NULL || url[0] == '\0') {
+    MG_ERROR(("null url"));
+  } else if ((c = mg_alloc_conn(mgr)) == NULL) {
+    MG_ERROR(("OOM"));
+  } else {
+    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
+    c->is_udp = (strncmp(url, "udp:", 4) == 0);
+    c->fd = (void *) (size_t) MG_INVALID_SOCKET;
+    c->fn = fn;
+    c->is_client = true;
+    c->fn_data = fn_data;
+    MG_DEBUG(("%lu %ld %s", c->id, c->fd, url));
+    mg_call(c, MG_EV_OPEN, (void *) url);
+    mg_resolve(c, url);
+  }
+  return c;
+}
+
+struct mg_connection *mg_listen(struct mg_mgr *mgr, const char *url,
+                                mg_event_handler_t fn, void *fn_data) {
+  struct mg_connection *c = NULL;
+  if ((c = mg_alloc_conn(mgr)) == NULL) {
+    MG_ERROR(("OOM %s", url));
+  } else if (!mg_open_listener(c, url)) {
+    MG_ERROR(("Failed: %s, errno %d", url, errno));
+    MG_PROF_FREE(c);
+    free(c);
+    c = NULL;
+  } else {
+    c->is_listening = 1;
+    c->is_udp = strncmp(url, "udp:", 4) == 0;
+    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
+    c->fn = fn;
+    c->fn_data = fn_data;
+    mg_call(c, MG_EV_OPEN, NULL);
+    if (mg_url_is_ssl(url)) c->is_tls = 1;  // Accepted connection must
+    MG_DEBUG(("%lu %ld %s", c->id, c->fd, url));
+  }
+  return c;
+}
+
+struct mg_connection *mg_wrapfd(struct mg_mgr *mgr, int fd,
+                                mg_event_handler_t fn, void *fn_data) {
+  struct mg_connection *c = mg_alloc_conn(mgr);
+  if (c != NULL) {
+    c->fd = (void *) (size_t) fd;
+    c->fn = fn;
+    c->fn_data = fn_data;
+    MG_EPOLL_ADD(c);
+    mg_call(c, MG_EV_OPEN, NULL);
+    LIST_ADD_HEAD(struct mg_connection, &mgr->conns, c);
+  }
+  return c;
+}
+
+struct mg_timer *mg_timer_add(struct mg_mgr *mgr, uint64_t milliseconds,
+                              unsigned flags, void (*fn)(void *), void *arg) {
+  struct mg_timer *t = (struct mg_timer *) calloc(1, sizeof(*t));
+  if (t != NULL) {
+    mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
+    t->id = mgr->timerid++;
+  }
+  return t;
+}
+
+long mg_io_recv(struct mg_connection *c, void *buf, size_t len) {
+  if (c->rtls.len == 0) return MG_IO_WAIT;
+  if (len > c->rtls.len) len = c->rtls.len;
+  memcpy(buf, c->rtls.buf, len);
+  mg_iobuf_del(&c->rtls, 0, len);
+  return (long) len;
+}
+
+void mg_mgr_free(struct mg_mgr *mgr) {
+  struct mg_connection *c;
+  struct mg_timer *tmp, *t = mgr->timers;
+  while (t != NULL) tmp = t->next, free(t), t = tmp;
+  mgr->timers = NULL;  // Important. Next call to poll won't touch timers
+  for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
+  mg_mgr_poll(mgr, 0);
+#if MG_ENABLE_FREERTOS_TCP
+  FreeRTOS_DeleteSocketSet(mgr->ss);
+#endif
+  MG_DEBUG(("All connections closed"));
+#if MG_ENABLE_EPOLL
+  if (mgr->epoll_fd >= 0) close(mgr->epoll_fd), mgr->epoll_fd = -1;
+#endif
+  mg_tls_ctx_free(mgr);
+}
+
+void mg_mgr_init(struct mg_mgr *mgr) {
+  memset(mgr, 0, sizeof(*mgr));
+#if MG_ENABLE_EPOLL
+  if ((mgr->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0)
+    MG_ERROR(("epoll_create1 errno %d", errno));
+#else
+  mgr->epoll_fd = -1;
+#endif
+#if MG_ARCH == MG_ARCH_WIN32 && MG_ENABLE_WINSOCK
+  // clang-format off
+  { WSADATA data; WSAStartup(MAKEWORD(2, 2), &data); }
+  // clang-format on
+#elif MG_ENABLE_FREERTOS_TCP
+  mgr->ss = FreeRTOS_CreateSocketSet();
+#elif defined(__unix) || defined(__unix__) || defined(__APPLE__)
+  // Ignore SIGPIPE signal, so if client cancels the request, it
+  // won't kill the whole process.
+  signal(SIGPIPE, SIG_IGN);
+#endif
+  mgr->pipe = MG_INVALID_SOCKET;
+  mgr->dnstimeout = 3000;
+  mgr->dns4.url = "udp://8.8.8.8:53";
+  mgr->dns6.url = "udp://[2001:4860:4860::8888]:53";
+  mg_tls_ctx_init(mgr);
+}
+
 #ifdef MG_ENABLE_LINES
 #line 1 "src/ota_dummy.c"
 #endif
@@ -6630,7 +6626,7 @@ int64_t mg_sntp_parse(const unsigned char *buf, size_t len) {
   return res;
 }
 
-static void sntp_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void sntp_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     int64_t milliseconds = mg_sntp_parse(c->recv.buf, c->recv.len);
     if (milliseconds > 0) {
@@ -6644,8 +6640,7 @@ static void sntp_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
     mg_sntp_request(c);
   } else if (ev == MG_EV_CLOSE) {
   }
-  (void) fnd;
-  (void) evd;
+  (void) ev_data;
 }
 
 void mg_sntp_request(struct mg_connection *c) {
@@ -7296,7 +7291,7 @@ static bool mg_socketpair(MG_SOCKET_TYPE sp[2], union usa usa[2]) {
 }
 
 // mg_wakeup() event handler
-static void wufn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void wufn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     unsigned long *id = (unsigned long *) c->recv.buf;
     // MG_INFO(("Got data"));
@@ -7316,7 +7311,7 @@ static void wufn(struct mg_connection *c, int ev, void *evd, void *fnd) {
     closesocket(c->mgr->pipe);         // When we're closing, close the other
     c->mgr->pipe = MG_INVALID_SOCKET;  // side of the socketpair, too
   }
-  (void) evd, (void) fnd;
+  (void) ev_data;
 }
 
 bool mg_wakeup_init(struct mg_mgr *mgr) {
@@ -13736,8 +13731,7 @@ static bool mg_ws_client_handshake(struct mg_connection *c) {
   return false;  // Continue event handler
 }
 
-static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data,
-                     void *fn_data) {
+static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data) {
   struct ws_msg msg;
   size_t ofs = (size_t) c->pfn_data;
 
@@ -13803,7 +13797,6 @@ static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data,
       }
     }
   }
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/mongoose.h b/mongoose.h
index ca54a243..aa4b815d 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -2096,7 +2096,7 @@ typedef uint64_t uECC_word_t;
 
 struct mg_connection;
 typedef void (*mg_event_handler_t)(struct mg_connection *, int ev,
-                                   void *ev_data, void *fn_data);
+                                   void *ev_data);
 void mg_call(struct mg_connection *c, int ev, void *ev_data);
 void mg_error(struct mg_connection *c, const char *fmt, ...);
 
diff --git a/src/dns.c b/src/dns.c
index 675f20de..0df92881 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -134,8 +134,7 @@ bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
   return true;
 }
 
-static void dns_cb(struct mg_connection *c, int ev, void *ev_data,
-                   void *fn_data) {
+static void dns_cb(struct mg_connection *c, int ev, void *ev_data) {
   struct dns_data *d, *tmp;
   struct dns_data **head = (struct dns_data **) &c->mgr->active_dns_requests;
   if (ev == MG_EV_POLL) {
@@ -189,7 +188,6 @@ static void dns_cb(struct mg_connection *c, int ev, void *ev_data,
       mg_dns_free(head, d);
     }
   }
-  (void) fn_data;
 }
 
 static bool mg_dns_send(struct mg_connection *c, const struct mg_str *name,
diff --git a/src/event.c b/src/event.c
index b50d246a..e6217f40 100644
--- a/src/event.c
+++ b/src/event.c
@@ -19,8 +19,8 @@ void mg_call(struct mg_connection *c, int ev, void *ev_data) {
   // Run user-defined handler first, in order to give it an ability
   // to intercept processing (e.g. clean input buffer) before the
   // protocol handler kicks in
-  if (c->fn != NULL) c->fn(c, ev, ev_data, c->fn_data);
-  if (c->pfn != NULL) c->pfn(c, ev, ev_data, c->pfn_data);
+  if (c->fn != NULL) c->fn(c, ev, ev_data);
+  if (c->pfn != NULL) c->pfn(c, ev, ev_data);
 }
 
 void mg_error(struct mg_connection *c, const char *fmt, ...) {
@@ -31,5 +31,5 @@ void mg_error(struct mg_connection *c, const char *fmt, ...) {
   va_end(ap);
   MG_ERROR(("%lu %ld %s", c->id, c->fd, buf));
   c->is_closing = 1;             // Set is_closing before sending MG_EV_CALL
-  mg_call(c, MG_EV_ERROR, buf);  // Let user handler to override it
+  mg_call(c, MG_EV_ERROR, buf);  // Let user handler override it
 }
diff --git a/src/event.h b/src/event.h
index 8fb521d5..12414379 100644
--- a/src/event.h
+++ b/src/event.h
@@ -2,7 +2,7 @@
 
 struct mg_connection;
 typedef void (*mg_event_handler_t)(struct mg_connection *, int ev,
-                                   void *ev_data, void *fn_data);
+                                   void *ev_data);
 void mg_call(struct mg_connection *c, int ev, void *ev_data);
 void mg_error(struct mg_connection *c, const char *fmt, ...);
 
diff --git a/src/http.c b/src/http.c
index c9488683..16608089 100644
--- a/src/http.c
+++ b/src/http.c
@@ -1,7 +1,7 @@
+#include "http.h"
 #include "arch.h"
 #include "base64.h"
 #include "fmt.h"
-#include "http.h"
 #include "json.h"
 #include "log.h"
 #include "net.h"
@@ -431,7 +431,7 @@ void mg_http_reply(struct mg_connection *c, int code, const char *headers,
   c->is_resp = 0;
 }
 
-static void http_cb(struct mg_connection *, int, void *, void *);
+static void http_cb(struct mg_connection *, int, void *);
 static void restore_http_cb(struct mg_connection *c) {
   mg_fs_close((struct mg_fd *) c->pfn_data);
   c->pfn_data = NULL;
@@ -445,10 +445,9 @@ char *mg_http_etag(char *buf, size_t len, size_t size, time_t mtime) {
   return buf;
 }
 
-static void static_cb(struct mg_connection *c, int ev, void *ev_data,
-                      void *fn_data) {
+static void static_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_WRITE || ev == MG_EV_POLL) {
-    struct mg_fd *fd = (struct mg_fd *) fn_data;
+    struct mg_fd *fd = (struct mg_fd *) c->pfn_data;
     // Read to send IO buffer directly, avoid extra on-stack buffer
     size_t n, max = MG_IO_SIZE, space;
     size_t *cl = (size_t *) &c->data[(sizeof(c->data) - sizeof(size_t)) /
@@ -973,7 +972,7 @@ static int skip_chunk(const char *buf, int len, int *pl, int *dl) {
   return i + 2 + n + 2;
 }
 
-static void http_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void http_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ || ev == MG_EV_CLOSE) {
     struct mg_http_message hm;
     size_t ofs = 0;  // Parsing offset
@@ -1035,10 +1034,10 @@ static void http_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
     }
     if (ofs > 0) mg_iobuf_del(&c->recv, 0, ofs);  // Delete processed data
   }
-  (void) evd, (void) fnd;
+  (void) ev_data;
 }
 
-static void mg_hfn(struct mg_connection *c, int ev, void *ev_data, void *fnd) {
+static void mg_hfn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/quit")) {
@@ -1053,7 +1052,7 @@ static void mg_hfn(struct mg_connection *c, int ev, void *ev_data, void *fnd) {
       mg_http_reply(c, 200, "", "hi\n");
     }
   } else if (ev == MG_EV_CLOSE) {
-    if (c->data[0] == 'X') *(bool *) fnd = true;
+    if (c->data[0] == 'X') *(bool *) c->fn_data = true;
   }
 }
 
diff --git a/src/mqtt.c b/src/mqtt.c
index 5301f586..8531424b 100644
--- a/src/mqtt.c
+++ b/src/mqtt.c
@@ -410,7 +410,8 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
       }
       if (p > end) return MQTT_MALFORMED;
       if (version == 5 && p + 2 < end) {
-        len_len = (uint32_t) decode_varint(p, (size_t) (end - p), &m->props_size);
+        len_len =
+            (uint32_t) decode_varint(p, (size_t) (end - p), &m->props_size);
         if (!len_len) return MQTT_MALFORMED;
         m->props_start = (size_t) (p + len_len - buf);
         p += len_len + m->props_size;
@@ -426,8 +427,7 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
   return MQTT_OK;
 }
 
-static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data,
-                    void *fn_data) {
+static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     for (;;) {
       uint8_t version = c->is_mqtt5 ? 5 : 4;
@@ -495,7 +495,6 @@ static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data,
     }
   }
   (void) ev_data;
-  (void) fn_data;
 }
 
 void mg_mqtt_ping(struct mg_connection *nc) {
diff --git a/src/sntp.c b/src/sntp.c
index 046ac6b5..b3f2962c 100644
--- a/src/sntp.c
+++ b/src/sntp.c
@@ -38,7 +38,7 @@ int64_t mg_sntp_parse(const unsigned char *buf, size_t len) {
   return res;
 }
 
-static void sntp_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void sntp_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     int64_t milliseconds = mg_sntp_parse(c->recv.buf, c->recv.len);
     if (milliseconds > 0) {
@@ -52,8 +52,7 @@ static void sntp_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
     mg_sntp_request(c);
   } else if (ev == MG_EV_CLOSE) {
   }
-  (void) fnd;
-  (void) evd;
+  (void) ev_data;
 }
 
 void mg_sntp_request(struct mg_connection *c) {
diff --git a/src/sock.c b/src/sock.c
index 4823caec..6d98dd2a 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -620,7 +620,7 @@ static bool mg_socketpair(MG_SOCKET_TYPE sp[2], union usa usa[2]) {
 }
 
 // mg_wakeup() event handler
-static void wufn(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void wufn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_READ) {
     unsigned long *id = (unsigned long *) c->recv.buf;
     // MG_INFO(("Got data"));
@@ -640,7 +640,7 @@ static void wufn(struct mg_connection *c, int ev, void *evd, void *fnd) {
     closesocket(c->mgr->pipe);         // When we're closing, close the other
     c->mgr->pipe = MG_INVALID_SOCKET;  // side of the socketpair, too
   }
-  (void) evd, (void) fnd;
+  (void) ev_data;
 }
 
 bool mg_wakeup_init(struct mg_mgr *mgr) {
diff --git a/src/ws.c b/src/ws.c
index 38f904db..7fc8b116 100644
--- a/src/ws.c
+++ b/src/ws.c
@@ -163,8 +163,7 @@ static bool mg_ws_client_handshake(struct mg_connection *c) {
   return false;  // Continue event handler
 }
 
-static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data,
-                     void *fn_data) {
+static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data) {
   struct ws_msg msg;
   size_t ofs = (size_t) c->pfn_data;
 
@@ -230,7 +229,6 @@ static void mg_ws_cb(struct mg_connection *c, int ev, void *ev_data,
       }
     }
   }
-  (void) fn_data;
   (void) ev_data;
 }
 
diff --git a/test/fuzz.c b/test/fuzz.c
index a0eb8d5a..5301c147 100644
--- a/test/fuzz.c
+++ b/test/fuzz.c
@@ -14,12 +14,11 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *, size_t);
 int LLVMFuzzerTestOneInput(const uint8_t *, size_t);
 #endif
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   struct mg_http_serve_opts opts = {.root_dir = "."};
   if (ev == MG_EV_HTTP_MSG) {
     mg_http_serve_dir(c, (struct mg_http_message *) ev_data, &opts);
   }
-  (void) fn_data;
 }
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
@@ -110,7 +109,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     const char *url = "http://localhost:12345";
     struct mg_connection *c = mg_http_connect(&mgr, url, fn, NULL);
     mg_iobuf_add(&c->recv, 0, data, size);
-    c->pfn(c, MG_EV_READ, NULL, NULL);
+    c->pfn(c, MG_EV_READ, NULL); // manually invoke protocol event handler
 
     mg_mgr_free(&mgr);
     free(pkt);
diff --git a/test/mip_tap_test.c b/test/mip_tap_test.c
index dcb8a93a..4fd1e3ef 100644
--- a/test/mip_tap_test.c
+++ b/test/mip_tap_test.c
@@ -59,18 +59,16 @@ struct Post_reply {
 };
 
 char *fetch(struct mg_mgr *mgr, const char *url, const char *post_data);
-static void f_http_fetch_query(struct mg_connection *c, int ev, void *ev_data,
-                               void *fn_data);
+static void f_http_fetch_query(struct mg_connection *c, int ev, void *ev_data);
 int get_response_code(char *);  // Returns HTTP status code from full char* msg
 
-static void f_http_fetch_query(struct mg_connection *c, int ev, void *ev_data,
-                               void *fn_data) {
+static void f_http_fetch_query(struct mg_connection *c, int ev, void *ev_data) {
   static char *http_response = 0;
   static bool http_response_allocated =
       0;  // So that we will update out parameter
   unsigned int http_responses_received = 0;
   struct Post_reply *post_reply_l;
-  post_reply_l = (struct Post_reply *) fn_data;
+  post_reply_l = (struct Post_reply *) c->fn_data;
 
   if (ev == MG_EV_CONNECT) {
     mg_printf(c, post_reply_l->post);
@@ -159,8 +157,7 @@ static void test_http_fetch(struct mg_mgr *mgr) {
 static struct mg_connection *s_conn;
 static char s_topic[16];
 
-static void mqtt_fn(struct mg_connection *c, int ev, void *ev_data,
-                    void *fn_data) {
+static void mqtt_fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_MQTT_OPEN) {
     // MQTT connect is successful
     struct mg_mqtt_opts sub_opts;
@@ -180,7 +177,7 @@ static void mqtt_fn(struct mg_connection *c, int ev, void *ev_data,
       ASSERT(0);
     if (mm->data.len != 2 || strcmp(mm->data.ptr, "hi")) ASSERT(0);
     mg_mqtt_disconnect(c, NULL);
-    *(bool *) fn_data = true;
+    *(bool *) c->fn_data = true;
   } else if (ev == MG_EV_CLOSE) {
     s_conn = NULL;
   }
diff --git a/test/mip_test.c b/test/mip_test.c
index 5e2dcdd9..a143b999 100644
--- a/test/mip_test.c
+++ b/test/mip_test.c
@@ -30,25 +30,25 @@ static void test_statechange(void) {
   onstatechange(&iface);
 }
 
-static void ph(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  if (ev == MG_EV_POLL) ++(*(int *) fn_data);
+static void ph(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_POLL) ++(*(int *) c->fn_data);
   (void) c, (void) ev_data;
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  (void) c, (void) ev, (void) ev_data, (void) fn_data;
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  (void) c, (void) ev, (void) ev_data;
 }
 
-static void frag_recv_fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void frag_recv_fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ERROR) {
     if (s_sent_fragment) {
       ASSERT(strcmp((char*) ev_data, "Received fragmented packet") == 0);
     }
   }
-  (void) c, (void) ev_data, (void) fn_data;
+  (void) c, (void) ev_data;
 }
 
-static void frag_send_fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void frag_send_fn(struct mg_connection *c, int ev, void *ev_data) {
   static bool s_sent;
   static int s_seg_sizes[] = {416, 416, 368};
   if (ev == MG_EV_POLL) {
@@ -60,7 +60,7 @@ static void frag_send_fn(struct mg_connection *c, int ev, void *ev_data, void *f
     // Checking TCP segment sizes (ev_data points to the TCP payload length)
     ASSERT(*(int *) ev_data == s_seg_sizes[s_seg_sent++]);
   }
-  (void) c, (void) ev_data, (void) fn_data;
+  (void) c, (void) ev_data;
 }
 
 static void test_poll(void) {
diff --git a/test/unit_test.c b/test/unit_test.c
index 79d1315a..a219b2a3 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -344,10 +344,10 @@ static void test_iobuf(void) {
   mg_iobuf_free(&io);
 }
 
-static void sntp_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
+static void sntp_cb(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_SNTP_TIME) {
-    int64_t received = *(int64_t *) evd;
-    *(int64_t *) fnd = received;
+    int64_t received = *(int64_t *) ev_data;
+    *(int64_t *) c->fn_data = received;
     MG_DEBUG(("got time: %lld", received));
 #if MG_ARCH == MG_ARCH_UNIX
     struct timeval tv = {0, 0};
@@ -409,16 +409,16 @@ struct mqtt_data {
 #define flags_released (1 << 3)
 #define flags_completed (1 << 4)
 
-static void mqtt_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
-  struct mqtt_data *test_data = (struct mqtt_data *) fnd;
+static void mqtt_cb(struct mg_connection *c, int ev, void *ev_data) {
+  struct mqtt_data *test_data = (struct mqtt_data *) c->fn_data;
   char *buf = test_data->msg;
 
   if (ev == MG_EV_MQTT_OPEN) {
-    buf[0] = *(int *) evd == 0 ? 'X' : 'Y';
+    buf[0] = *(int *) ev_data == 0 ? 'X' : 'Y';
   } else if (ev == MG_EV_CLOSE) {
     buf[0] = 0;
   } else if (ev == MG_EV_MQTT_CMD) {
-    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) evd;
+    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
     if (mm->cmd == MQTT_CMD_SUBACK) {
       test_data->flags = flags_subscribed;
     } else if (mm->cmd == MQTT_CMD_PUBACK) {  // here we assume the broker
@@ -431,7 +431,7 @@ static void mqtt_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
       test_data->flags |= flags_completed;
     }
   } else if (ev == MG_EV_MQTT_MSG) {
-    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) evd;
+    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
     snprintf(test_data->topic, test_data->topicsize, "%.*s",
              (int) mm->topic.len, mm->topic.ptr);
     snprintf(buf + 1, test_data->msgsize - 2, "%.*s", (int) mm->data.len,
@@ -686,8 +686,8 @@ static void test_mqtt(void) {
   test_mqtt_ver(5);
 }
 
-static void eh1(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct mg_tls_opts *topts = (struct mg_tls_opts *) fn_data;
+static void eh1(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_tls_opts *topts = (struct mg_tls_opts *) c->fn_data;
   if (ev == MG_EV_ACCEPT && topts != NULL) mg_tls_init(c, topts);
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
@@ -751,7 +751,6 @@ static void eh1(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
     mg_ws_send(c, wm->data.ptr, wm->data.len, WEBSOCKET_OP_BINARY);
   }
-  (void) fn_data;
 }
 
 struct fetch_data {
@@ -759,8 +758,8 @@ struct fetch_data {
   int code, closed;
 };
 
-static void fcb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct fetch_data *fd = (struct fetch_data *) fn_data;
+static void fcb(struct mg_connection *c, int ev, void *ev_data) {
+  struct fetch_data *fd = (struct fetch_data *) c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     snprintf(fd->buf, FETCH_BUF_SIZE, "%.*s", (int) hm->message.len,
@@ -827,8 +826,8 @@ static bool cmpheader(const char *buf, const char *name, const char *value) {
   return h != NULL && mg_strcmp(*h, mg_str(value)) == 0;
 }
 
-static void wcb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  int *p = (int *) fn_data;
+static void wcb(struct mg_connection *c, int ev, void *ev_data) {
+  int *p = (int *) c->fn_data;
   if (ev == MG_EV_WS_OPEN) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_str *wsproto = mg_http_get_header(hm, "Sec-WebSocket-Protocol");
@@ -848,7 +847,7 @@ static void wcb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   }
 }
 
-static void ew2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void ew2(struct mg_connection *c, int ev, void *ev_data) {
   size_t size = 65 * 1024 + 737;
   if (ev == MG_EV_WS_OPEN) {
     char *msg = (char *) calloc(1, size + 1);
@@ -866,7 +865,7 @@ static void ew2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
         if (wm->data.ptr[i] != 'A') ok = 0;
       }
       ASSERT(ok == 1);
-      *(int *) fn_data = 1;
+      *(int *) c->fn_data = 1;
     }
   }
 }
@@ -897,10 +896,10 @@ static void test_ws(void) {
   ASSERT(mgr.conns == NULL);
 }
 
-static void eh9(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void eh9(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ERROR) {
     ASSERT(!strcmp((char *) ev_data, "socket error"));
-    *(int *) fn_data = 7;
+    *(int *) c->fn_data = 7;
   }
   (void) c;
 }
@@ -1166,7 +1165,7 @@ static void test_http_server(void) {
   ASSERT(mgr.conns == NULL);
 }
 
-static void h4(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void h4(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     MG_INFO(("[%.*s %.*s] message len %d", (int) hm->method.len, hm->method.ptr,
@@ -1190,7 +1189,6 @@ static void h4(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, hm, &opts);
     }
   }
-  (void) fn_data;
 }
 
 static void test_http_404(void) {
@@ -1242,8 +1240,8 @@ static void test_tls(void) {
 #endif
 }
 
-static void f3(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  int *ok = (int *) fn_data;
+static void f3(struct mg_connection *c, int ev, void *ev_data) {
+  int *ok = (int *) c->fn_data;
   // MG_INFO(("%d", ev));
   if (ev == MG_EV_CONNECT) {
     // c->is_hexdumping = 1;
@@ -1358,27 +1356,27 @@ static void test_host_validation(void) {
 #endif
 }
 
-static void f4(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void f4(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     mg_printf(c, "HTTP/1.0 200 OK\n\n%.*s/%s", (int) hm->uri.len, hm->uri.ptr,
               "abcdef");
-    strcat((char *) fn_data, "m");
+    strcat((char *) c->fn_data, "m");
     c->is_draining = 1;
   } else if (ev == MG_EV_CLOSE) {
-    strcat((char *) fn_data, "c");
+    strcat((char *) c->fn_data, "c");
   }
 }
 
-static void f4c(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void f4c(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_CONNECT) {
     mg_printf(c, "GET /foo/bar HTTP/1.0\n\n");
   } else if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     ASSERT(mg_strcmp(hm->body, mg_str("/foo/bar/abcdef")) == 0);
-    strcat((char *) fn_data, "m");
+    strcat((char *) c->fn_data, "m");
   } else if (ev == MG_EV_CLOSE) {
-    strcat((char *) fn_data, "c");
+    strcat((char *) c->fn_data, "c");
   }
 }
 
@@ -1398,11 +1396,11 @@ static void test_http_no_content_length(void) {
   ASSERT(mgr.conns == NULL);
 }
 
-static void f5(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void f5(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     mg_http_reply(c, 200, "", "%.*s", (int) hm->uri.len, hm->uri.ptr);
-    (*(int *) fn_data)++;
+    (*(int *) c->fn_data)++;
   }
 }
 
@@ -1616,7 +1614,7 @@ static void test_http_parse(void) {
   }
 }
 
-static void ehr(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void ehr(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_http_serve_opts opts;
@@ -1624,7 +1622,6 @@ static void ehr(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     opts.root_dir = "./test/data";
     mg_http_serve_dir(c, hm, &opts);
   }
-  (void) fn_data;
 }
 
 static void test_http_range(void) {
@@ -2109,10 +2106,10 @@ static void test_str(void) {
   }
 }
 
-static void fn1(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn1(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_ERROR) {
-    free(*(char **) fn_data);  // See #2263
-    *(char **) fn_data = mg_mprintf("%s", (char *) ev_data);
+    free(*(char **) c->fn_data);  // See #2263
+    *(char **) c->fn_data = mg_mprintf("%s", (char *) ev_data);
   }
   (void) c;
 }
@@ -2329,7 +2326,7 @@ static void test_crc32(void) {
   ASSERT(mg_crc32(mg_crc32(0, "ab", 2), "c", 1) == 891568578);
 }
 
-static void us(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void us(struct mg_connection *c, int ev, void *ev_data) {
   struct mg_http_message *hm = (struct mg_http_message *) ev_data;
   if (ev == MG_EV_HTTP_MSG && mg_http_match_uri(hm, "/upload")) {
     MG_DEBUG(("Got all %lu bytes!", (unsigned long) hm->body.len));
@@ -2340,11 +2337,10 @@ static void us(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_HTTP_MSG) {
     mg_http_reply(c, 200, "", "ok\n");
   }
-  (void) fn_data;
 }
 
-static void uc(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  const char **s = (const char **) fn_data;
+static void uc(struct mg_connection *c, int ev, void *ev_data) {
+  const char **s = (const char **) c->fn_data;
   if (ev == MG_EV_OPEN) {
     // c->is_hexdumping = 1;
   } else if (ev == MG_EV_CONNECT) {
@@ -2360,7 +2356,6 @@ static void uc(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     ASSERT(mg_strcmp(hm->body, mg_str(*s)) == 0);
     *s = NULL;
   }
-  (void) fn_data;
 }
 
 static void test_http_upload(void) {
@@ -2380,7 +2375,7 @@ static void test_http_upload(void) {
 
 #define LONG_CHUNK "chunk with length taking up more than two hex digits"
 
-static void eX(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void eX(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     mg_printf(c, "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
     c->data[0] = 1;
@@ -2398,10 +2393,10 @@ static void eX(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       c->data[0] = 0;
     }
   }
-  (void) ev_data, (void) fn_data;
+  (void) ev_data;
 }
 
-static void eY(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void eY(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     mg_printf(c, "HTTP/1.1 200 OK\r\nContent-Length: 4\r\n\r\n");
     c->data[0] = 1;
@@ -2411,19 +2406,19 @@ static void eY(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     if (c->data[0] == 12) mg_send(c, "bc", 2);
     if (c->data[0] == 30) mg_send(c, "d", 1), c->is_resp = 0, c->data[0] = 0;
   }
-  (void) ev_data, (void) fn_data;
+  (void) ev_data;
 }
 
-static void eZ(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void eZ(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     mg_http_reply(c, 200, "", "abcd");
   }
-  (void) ev_data, (void) fn_data;
+  (void) ev_data;
 }
 
 // Do not delete chunks as they arrive
-static void eh4(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  uint32_t *crc = (uint32_t *) fn_data;
+static void eh4(struct mg_connection *c, int ev, void *ev_data) {
+  uint32_t *crc = (uint32_t *) c->fn_data;
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     *crc = mg_crc32(*crc, hm->body.ptr, hm->body.len);
@@ -2486,8 +2481,8 @@ struct stream_status {
 };
 
 // Consume recv buffer after letting it reach MG_MAX_RECV_SIZE
-static void eh8(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  struct stream_status *status = (struct stream_status *) fn_data;
+static void eh8(struct mg_connection *c, int ev, void *ev_data) {
+  struct stream_status *status = (struct stream_status *) c->fn_data;
   if (c->is_listening) return;
 
   ASSERT(c->recv.len <= MG_MAX_RECV_SIZE);
@@ -2523,19 +2518,17 @@ static void eh8(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
 }
 
 // Toggle c->is_full to prevent max_recv_buf_size reached read errors
-static void eh10(struct mg_connection *c, int ev, void *ev_data,
-                 void *fn_data) {
+static void eh10(struct mg_connection *c, int ev, void *ev_data) {
   if (c->recv.len >= MG_MAX_RECV_SIZE && ev == MG_EV_READ) c->is_full = true;
 
-  eh8(c, ev, ev_data, fn_data);
+  eh8(c, ev, ev_data);
 
   if (c->recv.len < MG_MAX_RECV_SIZE && ev == MG_EV_POLL) c->is_full = false;
 }
 
 // Send buffer larger than MG_MAX_RECV_SIZE to server
-static void eh11(struct mg_connection *c, int ev, void *ev_data,
-                 void *fn_data) {
-  struct stream_status *status = (struct stream_status *) fn_data;
+static void eh11(struct mg_connection *c, int ev, void *ev_data) {
+  struct stream_status *status = (struct stream_status *) c->fn_data;
   if (ev == MG_EV_CONNECT) {
     size_t len = MG_MAX_RECV_SIZE * 2;
     struct mg_iobuf buf = {NULL, 0, 0, 0};
@@ -2548,7 +2541,6 @@ static void eh11(struct mg_connection *c, int ev, void *ev_data,
     mg_iobuf_free(&buf);
   }
   (void) ev_data;
-  (void) fn_data;
 }
 
 static void test_http_stream_buffer(void) {
@@ -2601,7 +2593,7 @@ static void test_multipart(void) {
   ASSERT(mg_http_next_multipart(mg_str(s), ofs, &part) == 0);
 }
 
-static void eh7(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void eh7(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_http_serve_opts sopts;
@@ -2610,7 +2602,6 @@ static void eh7(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     sopts.fs = &mg_fs_packed;
     mg_http_serve_dir(c, hm, &sopts);
   }
-  (void) fn_data;
 }
 
 static void test_packed(void) {
@@ -2655,14 +2646,14 @@ int send(int sock, const void *buf, size_t len, int flags) {
 }
 #endif
 
-static void u1(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void u1(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_CONNECT) {
-    ((int *) fn_data)[0] += 1;
+    ((int *) c->fn_data)[0] += 1;
     mg_send(c, "hi", 2);
   } else if (ev == MG_EV_WRITE) {
-    ((int *) fn_data)[0] += 100;
+    ((int *) c->fn_data)[0] += 100;
   } else if (ev == MG_EV_READ) {
-    ((int *) fn_data)[0] += 10;
+    ((int *) c->fn_data)[0] += 10;
     mg_iobuf_free(&c->recv);
   }
   (void) ev_data;
@@ -2698,7 +2689,7 @@ static void test_check_ip_acl(void) {
          -1);  // not yet supported
 }
 
-static void w3(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void w3(struct mg_connection *c, int ev, void *ev_data) {
   // MG_INFO(("ev %d", ev));
   if (ev == MG_EV_WS_OPEN) {
     char buf[8192];
@@ -2711,20 +2702,20 @@ static void w3(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
   } else if (ev == MG_EV_WS_MSG) {
     struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
     ASSERT(mg_strcmp(wm->data, mg_str("lebowski")) == 0);
-    ((int *) fn_data)[0]++;
+    ((int *) c->fn_data)[0]++;
   } else if (ev == MG_EV_CLOSE) {
-    ((int *) fn_data)[0] += 10;
+    ((int *) c->fn_data)[0] += 10;
   }
 }
 
-static void w2(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void w2(struct mg_connection *c, int ev, void *ev_data) {
   struct mg_str msg = mg_str_n("lebowski", 8);
   if (ev == MG_EV_HTTP_MSG) {
     mg_ws_upgrade(c, (struct mg_http_message *) ev_data, NULL);
   } else if (ev == MG_EV_WS_OPEN) {
     mg_ws_send(c, "x", 1, WEBSOCKET_OP_PONG);
   } else if (ev == MG_EV_POLL && c->is_websocket) {
-    size_t ofs, n = (size_t) fn_data;
+    size_t ofs, n = (size_t) c->fn_data;
     if (n < msg.len) {
       // Send "msg" char by char using fragmented frames
       // mg_ws_send() sets the FIN flag in the WS header. Clean it
@@ -2771,7 +2762,7 @@ static void test_ws_fragmentation(void) {
   ASSERT(mgr.conns == NULL);
 }
 
-static void h7(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void h7(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_http_serve_opts opts;
@@ -2779,7 +2770,6 @@ static void h7(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     opts.root_dir = "./test/data,/foo=./src";
     mg_http_serve_dir(c, hm, &opts);
   }
-  (void) fn_data;
 }
 
 static void test_rewrites(void) {
@@ -3111,8 +3101,8 @@ static void test_rpc(void) {
   ASSERT(head == NULL);
 }
 
-static void ph(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  if (ev == MG_EV_POLL) ++(*(int *) fn_data);
+static void ph(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_POLL) ++(*(int *) c->fn_data);
   (void) c, (void) ev_data;
 }