Bind multicast receiver to INADDR_ANY on Windows, because binding to multicast group IPs doesn't seem to work. Use a different port number for (4351) multicast receiver commands to avoid multicast publisher packets ending up in the receiver (loopback issue).

src/conf.c

@@ -208,7 +208,7 @@ static const struct confparams frontend_cfg_params[] =
     {
         TOK_MULTICAST_CMD_PORT, "multicast_cmd_port", "Multicast command server UDP port",
         "Multicast data UDP port for sending commands to rig",
-        "4532", RIG_CONF_NUMERIC, { .n = { 0, 1000000, 1 } }
+        "4531", RIG_CONF_NUMERIC, { .n = { 0, 1000000, 1 } }
     },
 
     { RIG_CONF_END, NULL, }

src/network.c

@@ -996,8 +996,6 @@ void *multicast_receiver(void *arg)
     rig_debug(RIG_DEBUG_VERBOSE, "%s(%d): Starting multicast receiver\n", __FILE__,
             __LINE__);
 
-// Not working right now
-#if 0
     int optval = 1;
     if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0)
     {
@@ -1005,11 +1003,25 @@ void *multicast_receiver(void *arg)
                 strerror(errno));
         return NULL;
     }
+
+#if defined(SO_REUSEPORT)
+    // Windows does not have SO_REUSEPORT. However, SO_REUSEADDR works in a similar way.
+    if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval)) < 0)
+    {
+        rig_debug(RIG_DEBUG_ERR, "%s: error enabling UDP port reuse: %s\n", __func__,
+                strerror(errno));
+        return NULL;
+    }
 #endif
 
     memset(&dest_addr, 0, sizeof(dest_addr));
     dest_addr.sin_family = AF_INET;
+#ifdef __MINGW32__
+    // Windows cannot bind to multicast group addresses for some unknown reason
+    dest_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+#else
     dest_addr.sin_addr.s_addr = inet_addr(args->multicast_addr);
+#endif
     dest_addr.sin_port = htons(args->multicast_port);
 
     if (bind(socket_fd, (struct sockaddr *) &dest_addr, sizeof(dest_addr)) < 0)
@@ -1022,7 +1034,7 @@ void *multicast_receiver(void *arg)
     struct ip_mreq mreq;
     memset(&mreq, 0, sizeof(mreq));
     mreq.imr_multiaddr.s_addr = inet_addr(args->multicast_addr);
-    mreq.imr_interface.s_addr = INADDR_ANY;
+    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
 
     if (setsockopt(socket_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
     {

src/rig.c

@@ -674,7 +674,7 @@ RIG *HAMLIB_API rig_init(rig_model_t rig_model)
     rs->multicast_data_addr = "224.0.0.1"; // enable multicast data publishing by default
     rs->multicast_data_port = 4532;
     rs->multicast_cmd_addr = "224.0.0.2"; // enable multicast command server by default
-    rs->multicast_cmd_port = 4532;
+    rs->multicast_cmd_port = 4531;
     rs->lo_freq = 0;
     rs->cache.timeout_ms = 500;  // 500ms cache timeout by default
     rs->cache.ptt = 0;