Have you looked at shtoom? http://www.divmod.org/Home/Projects/Shtoom/ If your traffic is UDP, I'd recommend using STUN for the client. For the server, "all available local IPs" is a fairly vague question. IPv4? IPv6? With or without internet connectivity? Internal or external IPs? Some of these questions aren't even answerable. Usually if you want to provide advanced server configuration informations with regard to domain names and IP addresses you need to tell the server about them directly, with a config file of some sort. It varies by protocol what that file has to say.
Thanks yeah I've looked quite a bit at Shtoom. I guess my question was fairly vague, I simply meant a method to determine all available internal IP4 addresses. I did consider systems such as STUN and such, however I am multicasting so the system won't work across the Internet or NAT anyway (thankfully as it makes it all lot simpler).