I've just checked in multicast support into CVS. reactor.listenMulticast/reactor.connectMulticast, otherwise it's just like the new UDP stuff, except the transport has a new set of methods documented in twisted.internet.interfaces.IMulticastTransport.

As with the UDP API, I've never actually used multicast. Any comments from people who actually have used this in the past or can test this or whatever would be very welcome.