JFirewallTest is a free Java webstart application that tests for holes or open ports in your firewall.

Unlike other solutions, JFirewallTest is a two stage testing procedure that tests all 65,536 ports very rapidly.

After testing is complete, JFirewallTest will present a page of results reporting exactly what ports are open and accessible to others on the Internet. The list includes information about common services associated with each port and an estimate of the vulnerability.

JFirewallTest can be launched directly from this web page and will run on Windows, Linux and Mac computers.

JFirewallTest was developed to prove that testing all network ports does not need to take hours as suggested by many security web sites. Using a simple two phase approach JFirewallTest completes a full TCP port scan in under 10 minutes.

The first stage is to create a list of ports that are waiting for connections locally. JFirewallTest performs this action by making dummy connections to all ports on your local machine. To speed up operation JFirewallTest uses multiple threads and is therefore not slowed down by pending responses. The list of open ports is sent to this web site for the second stage.

The second stage is to test each open port to see if it is accessible from the Internet. This is performed by a cgi script on this server and the results are displayed live to the user.