Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
CocoaAsyncSocket worked well for me. I used both the TCP and UDP sockets, both listener and sender. Bandwidth, latency, and ease of use were all quite good.

Does that mean it will work for you? Can't tell. Since you haven't said anything about what you intend to do, nor your network programming experience, only you can decide.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.