Telnet is the standard Internet application protocol for remote login. It provides the encoding rules to link a user's keyboard/display on a client ("user") system with a command interpreter on a remote server system. A subset of the Telnet protocol is also incorporated within other application protocols, e.g., FTP and SMTP.
Telnet uses a single TCP connection, and its normal data stream ("Network Virtual Terminal" or "NVT" mode) is 7-bit ASCII with escape sequences to embed control functions. Telnet also allows the negotiation of many optional modes and functions.
The primary Telnet specification is to be found in RFC-854 [TELNET:1], while the options are defined in many other RFCs; see Section 7 for references.