IBGerm

CanYouSeeMe.org’s open port check tool is a simple but useful web-based utility for figuring out if your ISP or firewall is blocking certain ports you need to get things done on your computer. It’s a handy way to determine if connection issues you’re having—like difficulty sending email or trouble accessing an instant messaging client—are a problem with your internet connection or the computer itself.

CanYouSeeMe.org

The pared down webapp is useful for running a quick check to see if a port you need is open. For a more robust look at your accessible ports, check out  MyPorts to get detailed information on any open port, including its state, remote IP address, and app that’s currently using it.

MyPorts is a free download, Windows only.

MyPorts [via gHacks]