if, by file sharing u mean something similar to napster, then you need to create a client and a server.
i don't know of any tutorials as such, but what i usaully do is download the source code of an app similar to what i want, and see how it's done.
a good place to go is http://acky.net/vb (or your case http://acky.net/vb/vbtcp).
if u want some help with the your project, email me([email protected])