Telnet

Telnet can be used to access other computers or network services. To do this, however, you must first enable the protocol in the Windows features.

Telnet is always required when you need to connect to another computer or network component. Everything takes place via the text-based command line. In the past, this was es­pe­cially helpful for sharing the services of mainframe computers. But even today, Telnet is still used to manage networks, use ap­plic­a­tions, and share databases, albeit less and less fre­quently.

Over many years, Telnet also played a crucial role for in­sti­tu­tions that work with large databases. For example, in libraries, the protocol was an ele­ment­ary building block of online cata­logues published in the 1980s, which are better known as OPAC (Online Public Access Catalog). Initially, these digital pub­lic­a­tion databases were still ac­cess­ible in the libraries’ local networks via terminals. As the Internet started becoming more and more suc­cess­ful, it was also possible to access them via locally usable web in­ter­faces, whose com­mu­nic­a­tion means was supported by the Telnet protocol in many cases.

Another de­ploy­ment scenario, for which Telnet clients were typical, was the access to text-based programs on an ap­plic­a­tion server. For example, the Free Internet Chess Server can still be used today via Telnet con­nec­tions. Using text input, you can select from the available opponents and also move your pieces around the board. Meanwhile, graphical in­ter­faces such as the Jin Applet or Javaboard, which enable playing pieces to be moved with the mouse, have replaced the text-based input.

Telnet has always been a practical protocol for network and server ad­min­is­trat­ors. The ability to remotely manage devices on the network is ideal for ad­min­is­tra­tion tasks, es­pe­cially because the protocol is supported by almost all devices. It can also be used to check the avail­ab­il­ity of certain ports or to detect errors on e-mail servers (SMTP, port 25) by sending an e-mail directly from the server. The Telnet solution is an effective method for con­fig­ur­ing servers e.g. a web server: changes to the directory structure, the file access rights, or the password, can be im­ple­men­ted quickly and easily.

Since Telnet con­nec­tions are prac­tic­ally standard TCP con­nec­tions, the client can be employed to use or test other services that rely on TCP as a transport protocol. For example, with a simple request, you can check the func­tion­al­ity of an HTTP server or (as mentioned earlier) the status of an email server.

This ver­sat­il­ity is enhanced by the fact that the con­nec­tion protocol can be used across platforms. There are only a few devices that do not support the official IETF standard. Whether or not the client and server computers rely on the same operating system is also ir­rel­ev­ant. A further advantage of Telnet is that it allows un­res­tric­ted access to a con­trolled system’s resources if per­mis­sion has been given.

However, Telnet has a high security risk: both the con­nec­tion setup and the data transfer are not encrypted when using the Telnet protocol. All in­form­a­tion you send can therefore be in­ter­cep­ted by third parties in plain text, including the login in­form­a­tion required for remote access. This means that hackers won’t have much trouble taking over the system. A secure al­tern­at­ive to Telnet is Secure Shell (SSH).

An overview of the ad­vant­ages and dis­ad­vant­ages:

The client must first be enabled on Microsoft operating systems from Windows Vista onwards. We explain step by step how to activate Telnet on Windows 10 and Windows 11.