The trick is you don't. If the firewall is set up correctly
You won't be able to do a thing about it.
You can set up a box outside network
and tunnel through it to the outside
world. It will work b/c your box is
initiating the connection.
People who want and need free internet access and not just P2P use this technique.
http://www.peacefire.org/circumvento...per.8-2003.htm