I've had a look at networking libraries recently for another project. I was very disappointed when I couldn't find an open* equivalent for networking. I ended up using this lib which, although old, was easy to get working, and it supposedly would work for Windows too. I seem to remember that, on iOS at least, you can use raw BSD sockets... so most networking libs should be fairly trivial to port.
Even if you don't use a library, it's possible to write quite a simple wrapper over both BSD Sockets and WinSock quite easily. There's a surprisingly small amount of work that you actually have to do. The majority of the work is in synchronising the world, which would have to be hand rolled anyway.