Maybe this little tool can't attract too much the attention of the community, but I think it's really useful.
Do you remember the Portqry.exe tool? It's a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues by querying a single TCP/IP port, an ordered list of ports, or a sequential range of ports.
The command line is not always so simple and immediate to use, so today MS has released an add-on User Interface utility for PortQry. You can download it from HERE.