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Telnet is an application layer protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. 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 was developed in 1969 beginning with RFC 15, extended in RFC 854, and standardized as Internet Engineering Task Force (IETF) Internet Standard STD 8, one of the first Internet standards. Historically, Telnet provided access to a command-line interface (usually, of an operating system) on a remote host. Most network equipment and operating systems with a configuration (including systems based on Windows NT). 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. The term ''telnet'' is also used to refer to the software that implements the client part of the protocol. Telnet client applications are available for virtually all computer platforms. ''Telnet'' is also used as a verb. ''To telnet'' means to establish a connection with the Telnet protocol, either with command line client or with a programmatic interface. For example, a common directive might be: "''To change your password, telnet to the server, log in and run the passwd command.''" Most often, a user will be ''telnetting'' to a Unix-like server system or a network device (such as a router) and obtaining a login prompt to a command line text interface or a character-based full-screen manager. ==History and standards== JUNAID Telnet is a client-server protocol, based on a reliable connection-oriented transport. 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, however, predates TCP/IP and was originally run over Network Control Program (NCP) protocols. Before March 5, 1973, Telnet was an ad hoc protocol with no official definition.〔RFC 318 — documentation of old ad hoc telnet protocol〕 Essentially, it used an 8-bit channel to exchange 7-bit ASCII data. Any byte with the high bit set was a special Telnet character. On March 5, 1973, a Telnet protocol standard was defined at UCLA〔RFC 495 — announcement of Telnet protocol〕 with the publication of two NIC documents: Telnet Protocol Specification, NIC #15372, and Telnet Option Specifications, NIC #15373. Because of negotiable options protocol architecture, many extensions were made for it, some of which have been adopted as Internet standards, IETF documents STD 27 through STD 32. Some extensions have been widely implemented and others are proposed standards on the IETF standards track (see below) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Telnet」の詳細全文を読む スポンサード リンク
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