Knowledgebase: Other
Using Telnet to Diagnose Communication Errors
Posted by James Johnston on 28 December 2007 09:31 AM

You can use Windows' Telnet Client to confirm whether or not communications are getting through to a specified server and port or not.

If you are using Windows Vista or Windows 7, the Telnet Client is disabled by default.  You can enable it by going to Control Panel | Programs | Programs and Features | Turn Windows features on or off, and enable the "Telnet Client" option.  It may take a couple minutes for the change to complete.

Press Windows-R to open the "Run" dialog, then type "cmd" in it and press OK.  This will open a command prompt window.  It will be a black window with some white text that says something like "C:\>".  This is a command prompt, similar to the old DOS operating system.  Please note that the text shown in your prompt may vary, this is not important.

At the prompt, type "telnet address port" where "address" is the IP address, computer name, or domain name you want to connect to (as appropriate), and "port" is the TCP/IP communications port you want to connect on, then press enter.

For example...

When troubleshooting the USB License Manager application to activate your MicroSurvey USB License Key:

C:\> telnet MicroSurveyLicenseServer.com 1433

When troubleshooting a connection to your USB Network License Server to run a MicroSurvey product:

C:\> telnet YourNetworkLicenseServer 8765

When troubleshooting OfficeSync (Office Manager or Job Monitor) communication errors:

C:\> telnet OfficeSyncServer.com 1433

After executing the telnet program, you will see one of two results:

1) The command prompt screen will go blank.

This means that nothing is blocking communications between your workstation and the specified server or address, on the specified port. You will not see any sort of "success" message etc, because we are not really connecting to a telnet server so there is no return message that will be displayed.  We are using telnet simply as a tool to test basic connectivity problems.

Press Ctrl-] to open the telnet prompt

At the telnet prompt, type quit. 

Microsoft Telnet> quit

Then at the command prompt, type exit.

C:\> exit

You can stop troubleshooting a connection problem. If you are still having some sort of connection errors in your application it is due to some other problem, and you should contact MicroSurvey Technical Support with further details.

or 2) You will see a connection error, something like "Could not open connection to the host on port x: Connect failed".

This confirms that something is blocking communications between your workstation and the specified computer or server, on the specified port.  Unfortunately this will not provide any further clues as to the source of the blockage; however, typical sources include personal firewall software running on your workstation (like Norton Personal Security, for example), enterprise firewall software running on your local network (like Microsoft ISA Server, for example), a hardware firewall, a router with integrated firewall features, a cable or ISDN modem with integrated firewall features, or even your Internet Service Provider (or their secondary providers) may be blocking specific communication ports.

Please contact your local IT or Network Support staff for further assistance as to any firewall software/firewall that may be present.  MicroSurvey Technical Support cannot help you determine this.

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