You might try SDL_net. It is free and cross-platform, and should cover both of your requirements:

• Server detection using UDP to broadcast to the local network (though which side does the broadcasting is a different conversation)
• Communication between server and client using TCP (if you care about sequencing and guaranteed transmission, and don't mind the wait) or UDP (if you don't care about those things and just want it to be fast)

That looks like it may work for me, would you know anywhere I can see what functions it has, and some basics on how to use them? Also, I don't really need it to be cross-platform, windows only works fine for me.

I would rather not double post, but I want at least somewhere I can go to find help for myself.

The library is documented decently from a "what functions are there" perspective.

Good network programming techniques are another topic altogether; an Internet search should uncover some decent guides. There are also some samples that come with the library, if code helps.

Then you're covered; the author provides Win32 binaries on the page I originally linked to.

This post was "where do I find a networking library"--I would consider a post about "how do I do <something specific> with TCP/UDP" an entirely different post, if that's what you mean.