+
+#ifdef PLATFORM_WINDOWS
+
+ /* https://msdn.microsoft.com/en-us/library/windows/desktop/ms739161%28v=vs.85%29.aspx
+ *
+ * ------------------------------------------------------------------------------
+ * Note The Winsock version of the IP_MULTICAST_LOOP option is
+ * semantically different than the UNIX version of the
+ * IP_MULTICAST_LOOP option:
+ *
+ * In Winsock, the IP_MULTICAST_LOOP option applies only to the receive path.
+ * In the UNIX version, the IP_MULTICAST_LOOP option applies to the send path.
+ *
+ * For example, applications ON and OFF (which are easier to track than
+ * X and Y) join the same group on the same interface; application ON
+ * sets the IP_MULTICAST_LOOP option on, application OFF sets the
+ * IP_MULTICAST_LOOP option off. If ON and OFF are Winsock
+ * applications, OFF can send to ON, but ON cannot sent to OFF. In
+ * contrast, if ON and OFF are UNIX applications, ON can send to OFF,
+ * but OFF cannot send to ON.
+ * ------------------------------------------------------------------------------
+ *
+ * Alles klar? Gut!
+ */
+
+ const int target_sock = sockin;
+#else
+ const int target_sock = sockout;
+#endif
+
+ if (::setsockopt (target_sock, IPPROTO_IP, IP_MULTICAST_LOOP, (char *) &loop, sizeof (loop)) < 0) {