Sometimes when running a program, you need to make sure a port is open to external or internal traffic. While programs that do not accept traffic do not
require opening a port to traffic, others do. If you are running a game server or a web server as a Windows service, you will have to open a port to allow traffic. Not opening a port for your server means that other people trying to access your server will not be able to do so.
The instructions for opening a port in your router vary widely
depending on your router and setup. The PortForward.com site offers instructions on a wide variety of routers and devices. Select your router to find instructions customised to your device.