Hi

ISP: Comcast
OS: OS X

When I checked port 81, it failed. so I would like to know the next step to find usable port.

Also, I would like to know if Port Checker needs
1) port 81 forwarding setting on router before test
and/or
2) local web server start at 81/80 before test.

Thanks,
Ken

Comcast has a list of well-known blocked ports. You may view it at http://businesshelp.comcast.com/help-and-support/internet/ports-blocked-on-comcast-network/.

Port 81 is not known to be blocked. You need to set up port forwarding in the router before you use the port check tool.