if i want to listen to a port ... and i am behind a router ... and i dont want to do port forwarding !!! ... how do i do that ... and how apps like bit torrents get out of that port forwarding stuff ? Thanks in Advance ...

AFAIK bit torrent doesn't get around port forwarding, you have to open ports to connect to the other users. If you don't open up the appropriate ports the only users you can connect to are the ones where you initiate the connection to who are not firewalled.

It's open source so you can check out the code.

You can't. But there are some other tricks that you can pull off that may or may not give you what you want.