UDP Multicast example:
http://ntrg.cs.tcd.ie/undergrad/4ba2/multicast/antony/example.html
How to multicast over TCP/IP
http://www.ibiblio.org/pub/linux/docs/howto/other-formats/html_single/Multicast-HOWTO.html
Linux Socket Multicast
http://www.tenouk.com/Module41c.html