How do programs like GNUtella and Bearshare use peer-to-peer file sharing? I want to make a simple file sharing program just for practice...but i cant find any types of documentation on how to do this. The main question is...how do get what IP addresses are linked to each other...? Anyone know where i can find documentations on how to do this?? Thanks!

have a look at freenet
it''s GPL and there is source available. This is one of the more complicated schemes out there. For your own exploration consider writing a simple server that outputs the last 10 IP addresses that have connected to it.

As a tip remember to write anything that connects to a socket communicate in plain ascii. The reason for this is so that you can telnet to your server and talk to it. Look at HTTP/SMTP/NNTP etc... then telnet to port 80 of a webserver and type the HTTP to get a page.

thanks a lot! yea...im just making something simple like that...its just gonna be for sharing text files among some peers...