Add mqtt_over_websocket_server example

Fixed bug in websocket handshake:
now adding Sec-WebSocket-Protocol header in handshake response.

PUBLISHED_FROM=e4a71ff9dc4aeec63db40cb7f356dc5b25c1215a

examples/mqtt_over_websocket_server/Makefile

@@ -0,0 +1,4 @@
+PROG = mqtt_over_websocket_server
+MODULE_CFLAGS = -DMG_ENABLE_MQTT_BROKER=1
+#SSL_LIB=mbedtls
+include ../examples.mk

examples/mqtt_over_websocket_server/mqtt_over_websocket_server.c

@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2014 Cesanta Software Limited
+ * All rights reserved
+ * This software is dual-licensed: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. For the terms of this
+ * license, see <http://www.gnu.org/licenses/>.
+ *
+ * You are free to use this software under the terms of the GNU General
+ * Public License, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * Alternatively, you can license this software under a commercial
+ * license, as set out in <https://www.cesanta.com/license>.
+ */
+
+#include "mongoose.h"
+
+static const char *s_mqtt_address = "0.0.0.0:1883";
+static const char *s_http_address = "0.0.0.0:8080";
+
+static void unproxy(struct mg_connection *c) {
+  struct mg_connection *pc = (struct mg_connection *) c->user_data;
+  if (pc != NULL) {
+    pc->flags |= MG_F_CLOSE_IMMEDIATELY;
+    pc->user_data = NULL;
+    c->user_data = NULL;
+  }
+  printf("Closing connection %p\n", c);
+}
+
+static void proxy_handler(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_POLL) return;
+  printf("%p %s EVENT %d %p\n", c, __func__, ev, ev_data);
+  switch (ev) {
+    case MG_EV_CLOSE: {
+      unproxy(c);
+      break;
+    }
+    case MG_EV_RECV: {
+      struct mg_connection *pc = (struct mg_connection *) c->user_data;
+      if (pc != NULL) {
+        mg_send_websocket_frame(pc, WEBSOCKET_OP_BINARY, c->recv_mbuf.buf,
+                                c->recv_mbuf.len);
+        mbuf_remove(&c->recv_mbuf, c->recv_mbuf.len);
+      }
+      break;
+    }
+  }
+}
+
+static void http_handler(struct mg_connection *c, int ev, void *ev_data) {
+  struct mg_connection *pc = (struct mg_connection *) c->user_data;
+  if (ev == MG_EV_POLL) return;
+  printf("%p %s EVENT %d %p\n", c, __func__, ev, ev_data);
+  /* Do your custom event processing here */
+  switch (ev) {
+    case MG_EV_WEBSOCKET_HANDSHAKE_DONE: {
+      pc = mg_connect(c->mgr, s_mqtt_address, proxy_handler);
+      pc->user_data = c;
+      c->user_data = pc;
+      printf("Created proxy connection %p\n", pc);
+      break;
+    }
+    case MG_EV_WEBSOCKET_FRAME: {
+      struct websocket_message *wm = (struct websocket_message *) ev_data;
+      if (pc != NULL) {
+        printf("Forwarding %d bytes\n", (int) wm->size);
+        mg_send(pc, wm->data, wm->size);
+      }
+      break;
+    }
+    case MG_EV_CLOSE: {
+      unproxy(c);
+      break;
+    }
+  }
+}
+
+static void mqtt_handler(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_POLL) return;
+  printf("%p %s EVENT %d %p\n", c, __func__, ev, ev_data);
+  /* Do your custom event processing here */
+  switch (ev) {
+    case MG_EV_CLOSE:
+      printf("Closing MQTT connection %p\n", c);
+      break;
+  }
+  mg_mqtt_broker(c, ev, ev_data);
+}
+
+static void start_mqtt_server(struct mg_mgr *mgr, const char *addr) {
+  struct mg_connection *c;
+  static struct mg_mqtt_broker brk;  // static is important - must not perish
+  if ((c = mg_bind(mgr, addr, mqtt_handler)) == NULL) {
+    fprintf(stderr, "Cannot start MQTT server on port [%s]\n", addr);
+    exit(EXIT_FAILURE);
+  }
+  mg_mqtt_broker_init(&brk, NULL);
+  c->user_data = &brk;
+  mg_set_protocol_mqtt(c);
+  printf("MQTT server started on %s\n", addr);
+}
+
+static void start_http_server(struct mg_mgr *mgr, const char *addr) {
+  struct mg_connection *c;
+  if ((c = mg_bind(mgr, addr, http_handler)) == NULL) {
+    fprintf(stderr, "Cannot start HTTP server on port [%s]\n", addr);
+    exit(EXIT_FAILURE);
+  }
+  mg_set_protocol_http_websocket(c);
+  printf("HTTP server started on %s\n", addr);
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  mg_mgr_init(&mgr, NULL);
+  start_http_server(&mgr, s_http_address);
+  start_mqtt_server(&mgr, s_mqtt_address);
+  for (;;) {
+    mg_mgr_poll(&mgr, 1000);
+  }
+}