Simple Port Tester is a free program by PcWinTech.com to help users test if their ports are open with just a few clicks. Installer version also available.

The trick with testing if your port forwarding is working is to have something on your computer actually listening on the port. If nothing is listening on the port the test will fail no matter what. This program will open the port, listen for the connection and help ensure a proper and reliable test as to whether or not your port forwarding is working.

Download and run it. Put in the port you wish to test and hit begin, that's it!

The program now tests both TCP & UDP ports.