Add mqtt-server example

src/event.h

@@ -18,20 +18,20 @@ void mg_call(struct mg_connection *c, int ev, void *ev_data);
 void mg_error(struct mg_connection *c, const char *fmt, ...);
 
 enum {
-  MG_EV_ERROR,     // Error                        char *error_message
-  MG_EV_POLL,      // mg_mgr_poll iteration        unsigned long *millis
-  MG_EV_RESOLVE,   // Host name is resolved        NULL
-  MG_EV_CONNECT,   // Connection established       NULL
-  MG_EV_ACCEPT,    // Connection accepted          NULL
-  MG_EV_READ,      // Data received from socket    struct mg_str *
-  MG_EV_WRITE,     // Data written to socket       int *num_bytes_written
-  MG_EV_CLOSE,     // Connection closed            NULL
-  MG_EV_HTTP_MSG,  // HTTP request/response        struct mg_http_message *
+  MG_EV_ERROR,      // Error                        char *error_message
+  MG_EV_POLL,       // mg_mgr_poll iteration        unsigned long *millis
+  MG_EV_RESOLVE,    // Host name is resolved        NULL
+  MG_EV_CONNECT,    // Connection established       NULL
+  MG_EV_ACCEPT,     // Connection accepted          NULL
+  MG_EV_READ,       // Data received from socket    struct mg_str *
+  MG_EV_WRITE,      // Data written to socket       int *num_bytes_written
+  MG_EV_CLOSE,      // Connection closed            NULL
+  MG_EV_HTTP_MSG,   // HTTP request/response        struct mg_http_message *
   MG_EV_WS_OPEN,    // Websocket handshake done     NULL
   MG_EV_WS_MSG,     // Websocket message received   struct mg_ws_message *
-  MG_EV_MQTT_MSG,   // MQTT message                 struct mg_mqtt_message *
+  MG_EV_MQTT_CMD,   // MQTT low-level command       struct mg_mqtt_message *
+  MG_EV_MQTT_MSG,   // MQTT PUBLISH received        struct mg_mqtt_message *
   MG_EV_MQTT_OPEN,  // MQTT CONNACK received        int *connack_status_code
   MG_EV_SNTP_TIME,  // SNTP time received           struct timeval *
   MG_EV_USER,       // Starting ID for user events
 };
-