Configure the TCP Port Number Used by Telnet Server

Applies To: Windows 7, Windows 8, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Vista

You can use this procedure to change the port number that the Telnet Server service listens to for client requests.

By default, Telnet Server listens on TCP port 23. If you change this, you must inform your clients of the new number so that they can include it in their requests to connect. If your users do not request the correct port number when they try to connect, the connection attempt fails.

Membership in the local Administrators group, or equivalent, is the minimum required to complete this procedure.

To change the port number used by Telnet Server

  • At a command prompt, type the following, and then press ENTER:

    tlntadmn [\\server] **config port=**PortNumber

    • \\server

      The name of the computer running Telnet Server whose port number you want to change. If this parameter is not present, then the command runs against the Telnet Server service on the local computer.

    • **config port=**PortNumber

      Specifies that you want to change the port number to the value specified by PortNumber.

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Format Meaning


Information that the user must supply


Elements that the user must type exactly as shown

Between brackets ([])

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Additional considerations

  • Tlntadmn.exe must be run at a command prompt that was opened by using the Run as administrator option. If you do not run it at an elevated command prompt, you receive an Access is denied message.

  • The Tlntadmn.exe tool is installed with Telnet Server, so it might not be present on a computer that does not have Telnet Server installed.

  • You can determine the current port number used by Telnet Server by running the following command:

    tlntadmn [\\server]

    Windows displays several current settings, including the port number.

See Also


Enable the Telnet Server Service
Grant Access to a Telnet Server
Configure Telnet Server Authentication
Configure Telnet Server to Allow Administrator Access by using Password Authentication
Configure the Command Interpreter Used by the Telnet Server
Configure Idle Session Timeouts for Telnet Sessions
Configure the Number of Simultaneous Sessions Supported
Configure the Domain Used for User Name Authentication