Best windows Client Server lib

[janderson]

Hi,

I'm looking for a good network library for a project I'm considering 
starting.  Basically I need to be able to handle multiple users who 
would login then send messages and files back and forth with the server.

Has anyone done that?  What libraries are you using?  Anyone have any 
examples of performing the basic login procedure. I'd rather not start 
from scratch.

Cheers,
-Joel