Telnet

Telnet is a protocol that allows you to connect to remote computers (called hosts) over a TCP/IP network (such as the Internet). You use software called a telnet client on your computer to make a connection to a telnet server (i.e., the remote host). Once your telnet client establishes a connection to the remote host, your client becomes a virtual terminal, allowing you to communicate with the remote host from your computer. In most cases, you'll need to log into the remote host, which requires that you have an account on that system. Occasionally, you can log in as guest or public without having an account.

Telnet clients are available for all major operating systems.

Command-line telnet clients are built into most versions of Mac OS X, Windows (95 and later), Unix, and Linux. To use them, go to their respective command lines (i.e., the Terminal application in Mac OS X, the shell in Unix or Linux, or the DOS prompt in Windows), and then enter:

telnet host
Replace host with the name of the remote computer to which you wish to connect.

Telnet is a contraction of the two words Telecommunications Network, and is one of the major network protocols used on the Internet. It is one of the earliest network protocols, and one of the only original protocols still in common use on the internet. It was developed in 1969, with the RFC 15, and has evolved over the years to be a robust protocol, although with mounting security concerns it is often foregone in place of the secure SSH protocol.

Unlike the graphical interfaces of the HTTP protocol, which have given us the World Wide Web, telnet is a text-based protocol. The original purpose of telnet was to have an easy interface for terminals to interact with one another, using relatively simple command structures and accessible interfaces. Although still in use, telnet is rarely used by the majority of the internet-browsing public, who instead use HTTP browsers and email clients for the majority of their connections.

In the age before personal computers, anyone who wanted to use a computer generally had to access a terminal that was hooked up to a massive mainframe. Originally, each terminal was hooked up to only one machine, which led to a number of problems. For example, if one person needed to use a number of different machines, each of which specialized in a different task, they would need to physically go to each different terminal to do one job. This could be frustrating if the terminals were located throughout a large building, but was particularly maddening of the mainframe you needed to use was located at an institution in a different city or country from you.

The telnet protocol helped overcome this difficulty. By using a simple suite of commands, users could log in to a distant terminal and ask the mainframe there to undertake whatever processes they needed accomplished. The results would come back to them through telnet, and it was as though they were sitting in front of the terminal itself. In many ways, telnet helped revolutionize the way research was done, and helped build what would eventually become the internet we know today.

Of course, not all of the early uses for telnet were so practical. In fact, one of the ways in which telnet is still used to this day has its roots back in 1978, when a student at Essex University built on the earlier success of terminal games like Adventure and Zork to create a Multi-User Dungeon game, or MUD. These virtual environments, which include other varieties like MUSHes and MOOs, allow multiple people to connect to a terminal via the telnet protocol. Once there, they can play a collective game, often fantasy themed, by inputting text commands and reading the responses and inputs from other players. Although the use of MUDs has diminished with the advent of graphical Massively Multiplayer Online Role-Playing Games (MMORPGs), they still remain a major use of the telnet protocol, with hundreds of thousands of players worldwide.


Although at one point telnet was used widely as a protocol by network administrators and those who needed to deal with their servers, it is rarely used for this purpose anymore. In 1995, a researcher at the Helsinki University of Technology in Finland, fed up with the security holes in telnet which allowed for malicious password sniffing and attacks, built a new protocol to replace it. This protocol, the Secure Shell, or SSH, has most of the same features of telnet, but has much more robust security.

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.

How to Connect to a Telnet Server

Telnet is a program that allows to connect to and communicate with a remote server, sometimes referred to as a telnet server. You can execute the full range of commands on the remote sever using a telnet connection on your local computer. Telnet does not encrypt information (for example, passwords) sent over, and hence such a connection is not secure.

How to Set Up a Telnet Server

Telnet is a text-based program that allows you to connect to other computers remotely. In Windows Vista and 7, this program is available as part of the operating system, but not installed. To setup the Telnet server you must install the program and establish the group of users. You can then open the Telnet window and manually enter commands. The process is quite complex, but Telnet allows you to work on another computer remotely, just as if you were sitting right in front of it.