There are several ways of opening a listening port on your computer, each of which is depending on the modem or router you are using. You will first need to obtain your IP address and Default Gateway address. You do this by going to Start, Run, then typing ipconfig into the text box and hitting enter. A Command Prompt window will pop up displaying the information you need. You will then need to open your modem and router page and follow the instructions it contains to add or open a port, using the information you were given in your Command Prompt box.