How Does Telnet Work?

By April Sanders

What is Telnet?

Telnet is a TCP/IP protocol, triggered by user command, that allows you to access a remote computer. While obtaining files from a remote computer via FTP is common, Telnet actually goes one step further and allows you to log on as a regular user of the computer, with access to all data and programs that may be installed on that computer. Telnet is usually used for technical support purposes.In the early days of the Internet, Telnet was also used to connect with something called a free-net, which is just what it sounds like: an open-access computer system. This was in part because dial up modems were so slow, whereas Telnet worked a lot faster. With the advent of high speed internet providers, however, most free-nets have shut down.

How Telnet Works

Telnet uses software, installed on your computer, to create a connection with the remote host. The Telnet client (software), at your command, will send a request to the Telnet server (remote host). The server will reply asking for a user name and password. If accepted, the Telnet client will establish a connection to the host, thus making your computer a virtual terminal and allowing you complete access to the host's computer. Telnet requires the use of a user name and password, which means you need to have previously set up an account on the remote computer. In some cases, however, computers with Telnet will allow guests to log on with restricted access.

Does my Computer Have Telnet?

Every major computer operating system, including Unix, Linux, Mac OS and Windows, has Telnet capabilities and may even have Telnet built into them. To find out, open the command box in your system (for Windows, that would be the "run" function in the Start menu that opens the DOS prompt) and enter the command: TELNET HOST, with HOST being the name of the remote host computer with which you would like to connect.Interestingly, Windows Vista does not automatically run Telnet. To run Telnet on Vista, you must activate the application by going to your Start menu, click on the "Control Panel," click on "Programs," and choose "Turn Windows features on or off." A dialog box will appear, and you should see Telnet Client listed, with a box next to it. Click on the box to select Telnet, then click "OK" and wait until installation is complete.When you want to exit the Telnet application, you need to run the command prompt again on your own computer. Different operating systems use different commands to exit, such as QUIT, CLOSE and LOGOFF. Windows uses LOGOFF. If none of the commands work, you can try ABORT; however, this command serves only to end Telnet on your end, sometimes leaving it running on the remote host computer, so use ABORT only as your last option.

References & Resources