Telnet

RFC 855 (STD 8)

Telnet (Telecommunication Network ) is the name of a widely used network protocol in the Internet. This old and well known client / server protocol is based on a character-based data exchange via a TCP connection. Programs that implement the function of the terminal, often also called Telnet. Telnet consists of two services: Telnet Client and Telnet Server.

The Telnet protocol consists of a set of core functions and some extensions. The core protocol is described in the IETF documents RFC 854 and RFC 855 (STD 8). STD 8 describes some basic methods of the protocol and expansion options.

There are numerous extensions to the protocol, some of which were included as Internet standards. The IETF STD documents 27-32 describe these extensions.

Telnet clients are available on all major operating systems such as Linux, Unix, Mac OS, and on all network-enabled versions of Windows by default under the name telnet callable. A well-known free open source client is PuTTY.

Windows 7 includes a telnet client, which must first be activated. On a Windows Server 2008, the service must first be installed and started. For remote access, the user must also be added and the firewall are set so that the default port 23 is not blocked in the defined group " Telnet Client".

History

Telnet was invented in 1969 in the framework of the project ARPANET ( Advanced Research Projects Agency Network) with the aim of expensive computing time, application programs and databases can also take advantage away. It first came to use in 1974.

Purpose

Telnet is typically used for remote control of computers in the form of text-based input and output. Programs that use a graphical interface can be used with Telnet.

It can be both a remote device and an installed on a computer program, the controlling unit. The representation of the transmitted information can vary depending on the terminal.

Once the connection is established between the Telnet client and the Telnet server, the keystrokes are sent from the controlling terminal to the remote computer and transferred back from there turn texts to the terminal. The remote computer to transmit, for example, the text-based outputs of a program, such as an interface for inputting commands to the operating system. In this way, can be remotely controlled from a computer, another computer. This can even be done remotely over two steps.

Since the data exchange can be done in unencrypted Telnet and easily be read via a network sniffer, the encrypted service Secure Shell (SSH ) is used to remotely access other computers today usually used instead of the Telnet service, it being possible with SSH, a to gain comparable access to a remote system that can work equally.

The Telnet service itself is still used today primarily to gain access to network-enabled firmwares of different devices or micro computers that use because of technical restrictions operating systems with minimal functionality that does not allow the operation of an SSH server.

The Telnet service is inter alia for the following areas of use:

  • Access to a remote console with option to use all commands and programs that are running (for example UNIX or DOS shell) in text mode
  • Access to text -based applications on an application server
  • Access to public and university libraries
  • Database-Queries
  • Remote configuration of devices and output of operational data

Benefits

  • The client program replaces many programs of services that you want to use the internet.
  • There is a connection between two computers set up, even if they are running on different operating systems.
  • There is an access to all resources possible if the appropriate authorization is available.

Disadvantages

  • No security features - it will be sent passwords in plain text, for example.
  • Because full access hackers can have an easy time.
Remote Shell Kermit (protocol)
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