RedDrake

Hmm I'd say MSDN is the best reference you can get on that. If you plan to use it on games, then go through the DirectPlay API, otherwise, try learning WinSock 2.0, which looks quite a bit with socket programming on Unix. Guess you can get some nice tutorials about those at GameDev.net.

If he planes to use it on games, why not use RakNet library and not wory about window's or linux, and do it in high level