If you have a Westell (2100) modem, type in 192.168.1.254 into your browser of choice and click "expert mode" at the bottom left. Then click advanced configuration > services > custom service > port forwarding. Type whatever in the 'name' field, and your computers IP (not the routers IP) in the 'IP' field. Enter 8000 in the 'ports' field, select TCP, and your done.
If you have a router PM me and I'll help you get situated.