Verifying ports are listening

by Mitch Tulloch [Published on 26 June 2007 / Last Updated on 26 June 2007]

How to determine if a server is listening on a given port.

In the old days of server troubleshooting, we used to use Telnet to check whether our SMTP server was listening on port 25, our HTTP server was listening on port 80, and so on. Open a Telnet session and type a few appropriate commands and you’d get a response (or not). Nowadays however we have LDAP ports and all kinds of ports and who knows what commands these ports respond to? How can you verify then whether a particular port is listening or not on a server? PortQry 2.0 is your friend, check it out at You’ll also find PortQry on the Companion DVD of the Windows Vista Resource Kit, see


Mitch Tulloch was lead author for the Windows Vista Resource Kit from Microsoft Press, which is THE book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. For more information see

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