Certain computer video games may require you to use specific ports on your router during online play. If you're playing on a public computer or on a network that you didn't actually set up yourself, certain ports may have been blocked by the network administrator. You can check to see if a port on your network is blocked by using one of a few different websites.
Use Ping.eu. Ping is a website that checks to see if a particular port is open on your unique IP address. Copy the IP address that is printed at the top of the screen into the IP address box. Type the number of the port you are trying to check into the box and click "Go." The Ping.eu site will tell you whether or not that port is open.
Use CanYouSeeMe.org. Type the number of the port you want to check into the box labeled "What Port?" Computer video games will recommend a port that you should use for online play, so type the number you were recommended into the box. Click "Check" to determine whether the port you have specified has a status of "Open" or a status of "Blocked."
Use YouGetSignal.com. Click "Use Current IP" to automatically fill your computer's IP address into the "Remote Signal" box. Type the number of the port you're trying to check into the "Port Number" box. Click "Check" to determine whether the port you have specified has a status of "Open" or a status of "Blocked."