Lots of applications beyond web surfing and email (especially those with two-way traffic) require you to setup “port forwarding” to bypass your NAT broadband router. One site that has instructions for a great number of applications and routers is PortForward.com. They have great graphics that show you step by step what you need to change in your router settings for the specific application you want help with. Next time you need to know what ports to forward for a specific protocol or where to find the port forwarding settings on a specific router take a look at PortForward.com.
I’ve used Portforward myself, it’s a great site!