Hello everybody! After some more work I finally #ifdef'd every setsockopt which wouldn't work with UNIX-compliant headers in cygwin out, and so the program compiles. setsockopt( IP_ADD_MEMBERSHIP ) for some multicast addresses works (doesn't give an error) - but my application won't receive a packet. If I start a sniffer I see that the packets come around the network. This is NT4/SP5 with cygwin 1.3.10 + current gcc release. Can somebody help me please? Thanks in advance! Regards, Phil -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Bug reporting: http://cygwin.com/bugs.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/