How to configure telnet
Enable the Telnet Server Service
Applies To: Windows 7, Windows 8, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Vista
Telnet Server is a network service. When you install Windows 7, Windows Server 2008 R2, Windows Vista or Windows Server 2008, the files that make up the Telnet Server service are copied to your computer, but they are not yet operational. The Telnet service is disabled at first. You must enable the service by configuring the service to start when you need it. On a Telnet server that is regularly used, you might want to configure the service to start automatically every time Windows starts. You can also configure the Telnet Server service to start only when you start it manually.
Membership in the local Administrators group, or the equivalent, is the minimum required to complete these procedures.
- Open the Services MMC snap-in. Click Start, and then type services.msc in the Start Search box.
- If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
- Right-click Telnet, and then click Properties.
- In the Startup type list, select one of the following:
- Automatic (Delayed Start) to start Telnet Server after Windows starts and all boot processes have finished
- Automatic to start Telnet Server when Windows starts
- Manual to allow Telnet Server to be started and stopped when needed
- Disabled to prevent Telnet Server from running
- To start or stop the service, on the Telnet Properties dialog box, click Start or Stop. You can also start or stop the service on the main Services page by selecting Telnet in the list, and then using the start (triangle) and stop (square) icon buttons on the toolbar at the top of the page.
- Open an elevated command prompt. Right-click a Command Prompt shortcut, and then click Run as administrator.
- If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
- Type one of the following commands:
- To start Telnet Server, type net start telnet.
- To stop Telnet Server, type net stop telnet.
Configure the TCP Port Number Used by Telnet Server
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.
- At a command prompt, type the following, and then press ENTER:tlntadmn [\\server] config port=PortNumber
- \\serverThe 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= PortNumberSpecifies that you want to change the port number to the value specified by PortNumber.
Configure the Command Interpreter Used by the Telnet Server
You can use this procedure to change the command interpreter program used by the Telnet server and presented to users in their Telnet sessions.
By default, the command interpreter is %systemroot%\system32\cmd.exe. You can change it to any command interpreter by changing the registry value.
- Start the Registry Editor. Click Start, type regedit in the Start Search box, and then press ENTER.
- If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then clickContinue.
- Open the registry key:HKEY_LOCAL_MACHINE\Software\Microsoft\TelnetServer\1.0
- Double-click the Shell registry entry.
- In the Value data text box, type the full path and name of the command interpreter you want to use.
- Do not change the registry entry DefaultShell. Changing that value is not supported. Change only the value of theShell registry entry.
Configure Idle Session Timeouts for Telnet Sessions
You can use this procedure to change how long the Telnet Server service allows a Telnet session to remain idle before it drops the session.
The default idle session time-out duration is one hour.
- At a command prompt, type the following, and then press ENTER:tlntadmn [\\server] config timeoutactive={yes|no}
- At a command prompt, type the following, and then press ENTER:tlntadmn [\\server] config timeout=hh:mm:ss
Configure the Number of Simultaneous Sessions Supported
You can use this procedure to change the number of Telnet sessions the Telnet Server service will support.
By default, Telnet Server supports two simultaneous connections.
- At a command prompt, type the following, and then press ENTER:tlntadmn [\\server] config maxconn=Number:
- \\serverThe name of the computer running Telnet Server whose simultaneous connection limit you want to change. If this parameter is not present, then the command runs against the Telnet Server service installed on the local computer.
- config maxconn=NumberSpecifies the maximum number of connections. You must specify this number with a positive integer that is smaller than 10 million.
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