Definition of telnet in The Network Encyclopedia.

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What is Telnet?

A standard TCP/IP protocol for running programs on remote hosts. The term “telnet” also refers to the software (client or server component) that implements this protocol on a particular platform or system. Telnet is defined in Request for Comments (RFC) 854.

How Telnet Works

Telnet is a terminal emulation program, which is a command-line interface for issuing commands on a remote computer. A user running telnet client software can interactively run command-line applications on a remote host that is running the telnet service or daemon. The user enters information at the telnet client; this information is processed on the telnet server and its output is returned to the user. For example, if you use telnet to connect to a UNIX server, you can issue UNIX commands to remotely perform operations on that server.


Microsoft Windows NT includes a telnet client implemented as a Microsoft Windows application, but does not include telnet server software. Windows 2000 includes both a telnet client implemented as a command-line utility and telnet server software that supports up to 63 simultaneous client connections but is licensed to only provide up to two simultaneous client connections. If you require support for additional client connections, you should obtain the Windows Services for UNIX add-on pack for Windows 2000 Server.


You can use a telnet client to connect to a Web server on port 80 or a Simple Mail Transfer Protocol (SMTP) mail server on port 25 and issue Hypertext Transfer Protocol (HTTP) or SMTP commands directly to the server for troubleshooting purposes.