X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fmidi%2B%2B2%2Fipmidi_port.cc;h=fd5cb9a2395e727a457dda57104038439ea0429b;hb=466141229f0402c807902f9fc42446bd4416c600;hp=be271f40251f78b1bf1ae7787c4bdef03b0b9fd3;hpb=3fc50258b8b7d51898dd95eb19244cbc0f2675c5;p=ardour.git

diff --git a/libs/midi++2/ipmidi_port.cc b/libs/midi++2/ipmidi_port.cc
index be271f4025..fd5cb9a239 100644
--- a/libs/midi++2/ipmidi_port.cc
+++ b/libs/midi++2/ipmidi_port.cc
@@ -231,27 +231,43 @@ IPMIDIPort::open_sockets (int base_port, const string& ifname)
 	addrout.sin_addr.s_addr = ::inet_addr("225.0.0.37");
 	addrout.sin_port = htons (base_port);
 
-	int loop;
-	socklen_t size;
-	if (::getsockopt (sockin, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, &size)) {
-		::perror ("getsockopt(IP_MULTICAST_LOOP)");
-	} else {
-		cout << "********* 1. multicast loopback: " << loop << " size was " << size << endl;
-	}
-
 	// Turn off loopback...
-	loop = 0;
-	if (::setsockopt(sockout, IPPROTO_IP, IP_MULTICAST_LOOP, (char *) &loop, sizeof (loop)) < 0) {
+	int loop = 0;
+
+#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) {
 		::perror("setsockopt(IP_MULTICAST_LOOP)");
 		return false;
 	}
 
-	if (::getsockopt (sockin, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, &size)) {
-		::perror ("getsockopt(IP_MULTICAST_LOOP)");
-	} else {
-		cout << "********* 2. multicast loopback: " << loop << " size was " << size << endl;
-	}
-
 #ifndef PLATFORM_WINDOWS
 
 	if (fcntl (sockin, F_SETFL, O_NONBLOCK)) {
@@ -315,10 +331,6 @@ IPMIDIPort::parse (framecnt_t timestamp)
 	socklen_t slen = sizeof(sender);
 	int r = ::recvfrom (sockin, (char *) buf, sizeof(buf), 0, (struct sockaddr *) &sender, &slen);
 
-	if (r != 18) {
-		cout << "IPMIDI: received from socket: " << r << endl;
-	}
-
 	if (r >= 0) {
 
 		_parser->set_timestamp (timestamp);