Telnet, however, predates TCP/IP and was originally run over Network Control Program (NCP) protocols.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: Essentially, it used an 8-bit channel to exchange 7-bit ASCII data. 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.
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, extended in, 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. Telnet should not be confused with Telenet.