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How Telnet Works and Guide to Creating Telnet Connections

written by: George Garza•edited by: Lamar Stonecypher•updated: 9/3/2009

If you want to connect to a remote computer, without a lot of bells and whistles, then telnet is for you.

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    How the Telnet Application Works

    Telnet is an IP application-layer protocol (layer 7) that gives you a console session on a remote machine. It is one of the few remaining applications that has been heldover from the early days of networking. The console session is text-based, not GUI. The holdover to a text based command system is one of the features that makes it not very popular. However, with Telnet, you can connect, configure, or otherwise complete operations on a remote computer. You are expected to be able to manuver your way around the computer system as in the old (DOS) days.

    In general, you need two computers to make a telnet connection. You need a remote telnet server and the telnet client application on yours that will connect to it. TCP Port 23 is needed as the default port.

    As a connection and configuration program it is quite old. There are many other programs that can be used for remote connection such as MS Remote Desktop Connection, Ultra VNC, AnyPlace Control, PC Anywhere to name just a few programs. But some companies, like Cisco, still use it extensively since their routers and switches are configured using a command-line interface. It also has several security issues; the most glaring is that the authentication elements, the username and password, are passed over the network as clear text. So the system is vulnerable to a third party hacking, compromise, and intrusion.

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    How to Create a Telnet Connection

    To create a Telnet connection between a server and a client, there are three steps:

          • On an XP machines, you must first enable the Telnet service. Go to Start ->Run -> services.msc from the run prompt. This service is normally disabled by default.
          • Start the Telnet Server program on the host. On Server 2003, the Telnet Server is Tlntsvr.exe and it runs as a service. You have the option of setting an automatic configuration to start when the computer starts, or to start it manually. If you do not start the service, the client will not be able to make a connection.
          • Once the server is operational, run the Client program on the local computer. Go to the command prompt: Start -> run -> cmd and launch Telnet.exe. Next you must specify the host where you want to make a connection. This is easy to do, type Telnet -> ComputerName at the command prompt. You may be asked to authenticate to the machine. If so use the administrator account and password. If the authentication works, you are remotely connected.

          Telnet is a fast and easy program to work with. It is great for simple configuration modification. But for more complex configurations and remote connections, you should work with a GUI based program that will give you more control. Telnet is not a dead protocol. Cisco, for example, uses it widely in its router and switch maintenance operations; but there too it is all command line driven. But for the most part, many tech-professionals prefer to use a GUI remote management application tool to connect to other systems. These are more flexible and also more secure.