Obtain IP adress for MDNS automatically

tutorials/udp/mdns-server/main.c

@@ -3,23 +3,45 @@
 
 #include "mongoose.h"
 
+#ifdef ADVANCED_EXAMPLE
+static void mdns_ev_handler(struct mg_connection *c, int ev, void *ev_data);
+#endif
+
 int main(void) {
-  uint32_t response_ip = inet_addr("192.168.69.11");
   struct mg_mgr mgr;
   static struct mg_connection *c;
   mg_log_set(MG_LL_DEBUG);  // Set log level
   mg_mgr_init(&mgr);        // Initialise event manager
 
   // Desired name must NOT have any dots in it, nor a domain
+#ifndef ADVANCED_EXAMPLE
   c = mg_mdns_listen(&mgr, NULL, "Mongoose");  // Start mDNS server
+#else
+  c = mg_mdns_listen(&mgr, mdns_ev_handler, "Mongoose");  // Start mDNS server
+#endif
   if (c == NULL) return 1;
-  // if not using our built-in TCP/IP stack, pass the IP address you want to
-  // use as a response, this depends on your underlying TCP/IP stack and number
-  // of interfaces available
-  memcpy(c->data, &response_ip, sizeof(response_ip));
 
   for (;;) mg_mgr_poll(&mgr, 1000);  // Event loop
 
   mg_mgr_free(&mgr);
   return 0;
 }
+
+// When not using our built-in TCP/IP stack, Mongoose responds with the address
+// of the interface in which the request came in. If, for some reason, you want
+// to use some other address, catch the MG_EV_MDNS_REQ event for MG_DNS_RTYPE_A
+// requests, and fill your desired address
+#ifdef ADVANCED_EXAMPLE
+static void mdns_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_MDNS_REQ) {
+    struct mg_mdns_req *req = (struct mg_mdns_req *) ev_data;
+    if (req->rr->atype == MG_DNS_RTYPE_A) {
+      struct mg_addr myaddr;
+      memset(&myaddr, 0, sizeof(myaddr));
+      myaddr.addr.ip4 = MG_IPV4(1, 2, 3, 4);
+      req->addr = &myaddr;
+    }
+  }
+  (void) c;
+}
+#endif