Some of these extensions have been adopted as Internet standards, IETF documents STD 27 through STD 32. Many extensions were made for Telnet because of its negotiable options protocol architecture. On March 5, 1973, a Telnet protocol standard was defined at UCLA with the publication of two NIC documents: Telnet Protocol Specification, NIC 15372, and Telnet Option Specifications, NIC 15373. Any byte with the high bit set was a special Telnet character. Įssentially, it used an 8-bit channel to exchange 7-bit ASCII data. The primary function of a User TELNET, then, is to provide the means by which its users can 'hit' all the keys on that virtual teletype.
The TELNET protocol is based upon the notion of a virtual teletype, employing a 7-bit ASCII character set.
Telnet, however, predates TCP/IP and was originally run over Network Control Protocol (NCP).Įven though Telnet was an ad hoc protocol with no official definition until March 5, 1973, the name actually referred to Teletype Over Network Protocol as the RFC 206 (NIC 7176) on Telnet makes the connection clear: Typically, this protocol is used to establish a connection to Transmission Control Protocol (TCP) port number 23, where a Telnet server application (telnetd) is listening. Telnet is a client-server protocol, based on a reliable connection-oriented transport. For example, a common directive might be: " To change your password, telnet into the server, log in and run the passwd command." In most cases, a user would be telnetting into a Unix-like server system or a network device (such as a router). To telnet means to establish a connection using the Telnet protocol, either with a command line client or with a graphical interface. Telnet client applications are available for virtually all computer platforms.
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The term telnet is also used to refer to the software that implements the client part of the protocol. However, because of serious security concerns when using Telnet over an open network such as the Internet, its use for this purpose has waned significantly in favor of SSH. Historically, Telnet provided access to a command-line interface on a remote host. Telnet was developed in 1969 beginning with RFC 15, extended in RFC 855, and standardized as Internet Engineering Task Force (IETF) Internet Standard STD 8, one of the first Internet standards. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP). Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. A telnet client accessing the Busybox in a router.