What is a simple way in Windows to test if traffic gets through to a specific port on a remote machine?
I found a hiddem gem the other day from Microsoft that is designed for testing ports:
"Portqry.exe is a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues. Portqry.exe runs on Windows 2000-based computers, on Windows XP-based computers, and on Windows Server 2003-based computers. The utility reports the port status of TCP and UDP ports on a computer that you select. "
Which version of Windows? For Windows 8/Server 2012 and later, the following works in PowerShell:
Test-NetConnection 188.8.131.52 -Port 80
Some Googling will also turn up alternatives which use the .NET Framework directly (since PowerShell lets you do that) for systems running lower versions of Windows that won't have
If you're not averse to using third-party utilities, Nmap is also a very good friend to have and it works from the command line.
Use the telnet command to connect to the server on the specified port, and see if a connection can be established.
$ telnet my_server 25 220 my_server ESMTP Postfix
$ telnet my_server 23632 Connecting To my_server...Could not open connection to the host, on port 23632: Connect failed
the following command will list all ports in use on the machine...
The output contains the protocol, local address, foreign address and current state
Use netcat Windows port:
>nc -zvv www.google.com 80 www.google.com [184.108.40.206] 80 (http) open sent 0, rcvd 0 > >nc -zvv www.google.com 888 www.google.com [220.127.116.11] 888 (?): TIMEDOUT sent 0, rcvd 0: NOTSOCK >