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TELNET (TELecommunication NETwork) is a network protocol used on the Internet or local area network (LAN) connections. It was developed in 1969 beginning with RFC 15 and standardized as IETF STD 8, one of the first Internet standards. Telenet is the largest provider of broadband cable services in Belgium. ... In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication. ... “LAN” redirects here. ... The Internet Engineering Task Force (IETF) develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standard bodies; and dealing in particular with standards of the TCP/IP and Internet protocol suite. ... Two Internet Engineering Task Force standards proposed by Jonathan B. Postel and J.K. Reynolds from University of Southern California Information Sciences Institute in their Request for Comments published in May 1983. ...

The term telnet also refers to software which implements the client part of the protocol. TELNET clients have been available on most Unix systems for many years and are available for virtually all platforms. Most network equipment and OSs with a TCP/IP stack support some kind of TELNET service server for their remote configuration (including ones based on Windows NT). Recently, Secure Shell has begun to dominate remote access for Unix-based machines. Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. ... // An operating system (OS) is the software that manages the sharing of the resources of a computer. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ... Windows NT (New Technology) is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ...

"To telnet" is also used as a verb meaning to establish or use a TELNET or other interactive TCP connection, as in, "To change your password, telnet to the server and run the passwd command". It has been suggested that Verbal agreement be merged into this article or section. ... passwd is a tool on most Unix and Linux systems used to change a users password. ...

Most often, a user will be telneting to a Unix-like server system or a simple network device such as a switch. For example, a user might "telnet in from home to check his mail at school". In doing so, he would be using a telnet client to connect from his computer to one of his servers. Once the connection is established, he would then log in with his account information and execute operating system commands remotely on that computer, such as ls or cd.

On many systems, the client may also be used to make interactive raw-TCP sessions, even when that option is not available, telnet sessions are equivalent to raw TCP as long as byte 255 never appears in the data. The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ...

Protocol details

TELNET is a client-server protocol, based on a reliable connection-oriented transport. Typically this is TCP port 23, although TELNET predates TCP/IP and was originally run on NCP. A protocol in which there is a single server which listens for connections, usually on a specific port (if this is TCP, UDP, or a similar protocol), and one or more clients which connect to it. ... In computer networking, a reliable protocol is one that ensures data arrival via some internal method, as opposed to an unreliable protocol, which does not guarantee that all the data will arrive intact (or indeed, at all). ... A connection-oriented networking protocol is one which identifies traffic flows by some connection identifier rather than by explicitly listing source and destination addresses. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ... It has been suggested that this article or section be merged into Computer port (software). ... The Network Control Program (sometimes the abbreviation NCP is mistakenly expanded to Network Control Protocol, but this term is not found in the contemporary documentation) was the original protocol suite of the ARPANET. In NCP, the physical layer, the data link layer, and the network layer were all specified by...

The protocol has many extensions, some of which have been adopted as Internet standards. IETF standards STD 27 through STD 32 define various extensions, most of which are extremely common. Other extensions are on the IETF standards track as proposed standards. An Internet standard is a specification for an innovative internetworking technology or methodology, which the Internet Engineering Task Force (IETF) ratified as an open standard after the innovation underwent peer review. ...

Security

When TELNET was initially developed in 1969, most users of networked computers were in the computer departments of academic institutions, or at large private and government research facilities. In this environment, security was not nearly as much of a concern as it became after the bandwidth explosion of the 1990s. The rise in the number of people with access to the Internet, and by extension, the number of people attempting to crack other people's servers made encrypted alternatives much more necessary. For the band, see 1990s (band). ... A black-hat is a term in computing for someone who compromises the security of a system without permission from an authorized party, usually with the intent of accessing computers connected to the network. ... In information technology, a server is an application or device that performs services for connected clients as part of a client-server architecture. ...

Experts in computer security, such as SANS Institute, and the members of the comp.os.linux.security newsgroup recommend that the use of TELNET for remote logins should be discontinued under all normal circumstances, for the following reasons: This article describes how security can be achieved through design and engineering. ... The SANS Institute (SysAdmin, Audit, Networking, and Security) is a trade name owned by the for-profit Escal Institute of Advanced Technologies. ... A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ...

• TELNET, by default, does not encrypt any data sent over the connection (including passwords), and so it is often practical to eavesdrop on the communications and use the password later for malicious purposes; anybody who has access to a router, switch, or gateway located on the network between the two hosts where TELNET is being used can intercept the packets passing by and obtain login and password information (and whatever else is typed) with any of several common utilities like tcpdump and Wireshark.
• Most implementations of TELNET lack an authentication scheme that makes it possible to ensure that communication is carried out between the two desired hosts, and not intercepted in the middle.
• Commonly used TELNET daemons have several vulnerabilities discovered over the years.

These security-related shortcomings have seen the usage of the TELNET protocol drop rapidly, especially on the public Internet, in favor of a the ssh protocol, first released in 1995. SSH provides much of the functionality of telnet, with the addition of strong encryption to prevent sensitive data such as passwords from being intercepted, and public key authentication, to ensure that the remote computer is actually who it claims to be. “Encrypt” redirects here. ... This article is about a computer networking device. ... Electrical switches. ... It has been suggested that this article or section be merged into Gateway (telecommunications). ... tcpdump is a common computer network debugging tool that runs under the command line. ... It has been suggested that Ethereal (software) be merged into this article or section. ... It has been suggested that Mafia Fraud Attack be merged into this article or section. ... In Unix and other computer multitasking operating systems, a daemon is a computer program that runs in the background, rather than under the direct control of a user; they are usually instantiated as processes. ... In computer security, the word vulnerability refers to a weakness or other opening in a system. ... Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ... PKC, see PKC (disambiguation) Public-key cryptography is a form of modern cryptography which allows users to communicate securely without previously agreeing on a shared secret key. ...

As has happened with other early Internet protocols, extensions to the TELNET protocol provide TLS security and SASL authentication that address the above issues. However, most TELNET implementations do not support these extensions; and there has been relatively little interest in implementing these as SSH is adequate for most purposes. The main advantage of TLS-TELNET would be the ability to use certificate-authority signed server certificates to authenticate a server host to a client that does not yet have the server key stored. In SSH, there is a weakness in that the user must trust the first session to a host when it has not yet acquired the server key. Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. ... Simple Authentication and Security Layer (SASL) is a framework for authentication and authorization in Internet protocols. ...

Clients and servers designed to pass IBM 5250 data streams over Telnet generally do support SSL encryption, as SSH does not include 5250 emulation. Under OS/400, Port 992 is the default port for Secured Telnet. IBM 5250, originally, was a particular model of a terminal device sold with the IBM S/34 minicomputer system. ... ASIM can refer to: In computing and electronics: Secure Sockets Layer, a communications protocol, predecessor to Transport Layer Security Server-Side Language, a category of programming languages used on the web which execute on the server S/SL programming language Single Stuck Line, a fault model for digital circuits In...

Current status

As of the mid-2000s, while the TELNET protocol itself has been mostly superseded, TELNET clients are still used, often when diagnosing problems, to manually "talk" to other services without specialized client software. For example, it is sometimes used in debugging network services such as an SMTP, IRC or HTTP server, by serving as a simple way to send commands to the server and examine the responses. Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. ... Simple Mail Transfer Protocol (SMTP) is the de facto standard for email transmission across the Internet. ... “IRC” redirects here. ... HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ...

However, other software such as nc (netcat) or socat on Unix (or PuTTY on Windows) are finding greater favor with some system administrators for testing purposes, as they can be called with arguments not to send any terminal control handshaking data. Also netcat does not distort the 377 octet, which allows raw access to TCP socket, unlike any standard-compliant TELNET software. In computing, netcat is a network utility for reading from and writing to network connections on either TCP or UDP. It is designed in a thin and simple way, which makes it easy to incorporate in larger applications. ... PuTTY is a free software SSH, Telnet, rlogin, and raw TCP client. ... In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins. ...

TELNET is still very popular in enterprise networks to access host applications, e.g. on IBM Mainframes. For other uses, see IBM (disambiguation) and Big Blue. ... For other uses, see Mainframe. ...

TELNET is still widely used for administration of network elements, e.g., in commissioning, integration and maintenance of core network elements in mobile communication networks. Core networks do not actually do much in the telecommunications field. ... Mobile phones from various years Several mobile phones A mobile or cellular telephone is a long-range, portable electronic device for personal telecommunications over long distances. ...

TELNET is also heavily used for MUD games played over the Internet, as well as talkers, MUSHes, MUCKs, MOOes, and the resurgent BBS community. This article is about a type of online computer game. ... A talker is a MUD variant, a communication system precursor to MMORPGs and other virtual worlds such as Second Life. ... The login screen from M*U*S*H, the centre of development for PennMUSH. A MUSH (sometimes said to be an abbreviation for Multi-User Shared Hack, Habitat, Holodeck, or Hallucination, though these are backronyms) is a text-based online social medium to which multiple users are connected at the... Muck can refer to several different things: An Alternative Rock Band From Baltimore Muck(Band) A type of soil: Muck (soil) An island in Scotland: Muck, Scotland The kayak club of NUIM: MUCK, NUIM Kayak Club In gambling, a number of actions both legal and illegal: Muck (gambling) Other meanings... Look up moo in Wiktionary, the free dictionary. ... A bulletin board system or BBS is a computer system running software that allows users to dial into the system over a phone line and, using a terminal program, perform functions such as downloading software and data, uploading data, playing games, reading news, and exchanging messages with other users. ...

In the 2007 Microsoft Windows release, Windows Vista, Telnet.exe is no longer installed by default, but is still included as an installable feature.^[1] Windows Vista is a line of graphical operating systems used on personal computers, including home and business desktops, notebook computers, Tablet PCs, and media centers. ...

See also

• Reverse telnet
• Telnet 3270 (TN3270)
• HyTelnet
• Kermit
• NCSA Telnet

Reverse Telnet is a mean of connecting to a TTY line via a regular telnet connection. ... TN3270 Running on a Mac OS X System TN3270 is the remote-login protocol used by software that emulates the IBM 3270 model of mainframe computer terminal. ... // History HyTelnet (sometimes rendered Hytelnet or HyTELNET) was an early attempt to create a universal or at least simpler interface for the various Telnet-based information resources available before the World Wide Web. ... Kermit is a computer file transfer/management protocol and a set of communications software tools; it provides a consistent approach to file transfer, terminal emulation, script programming, and character set conversion across many different computer hardware and OS platforms. ... NCSA Telnet is an implementation of the TELNET protocol created at the University of Illinois National Center for Supercomputing Applications in 1986 and continuously developed until 1996. ...

References

1. ^ Windows Vista does not include Telnet...or does it? (May 2, 2006).

May 2 is the 122nd day of the year in the Gregorian calendar (123rd in leap years). ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

External links

• Telnet Options - The official list of assigned option numbers at iana.org
• telnet.org places List of publicly accessible TELNET servers
• BBS Corner - Telnet BBS Guide
• Telnet Interactions Described as a Sequence Diagram
• Telnet START-TLS Option draft-altman-telnet-starttls-02.txt 2006
• Telnet Basics A tutorial on telnet for beginners. Explains what telnet is and how to use it.
• ASCII Star Wars available through Telnet

Related RFCs Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

• RFC 854 TELNET protocol specification
• RFC 855 TELNET option specifications
• RFC 856 TELNET binary transmission
• RFC 857 TELNET echo option
• RFC 858 TELNET suppress Go Ahead option
• RFC 859 TELNET status option
• RFC 860 TELNET timing mark option
• RFC 861 TELNET extended options - list option
• RFC 885 Telnet end of record option
• RFC 1041 Telnet 3270 regime option
• RFC 1073 Telnet Window Size Option
• RFC 1079 Telnet terminal speed option

• RFC 1091 Telnet terminal-type option
• RFC 1096 Telnet X display location option
• RFC 1097 Telnet subliminal-message option
• RFC 1116 Telnet linemode option
• RFC 1205 5250 Telnet interface
• RFC 1372 Telnet remote flow control option
• RFC 2217 Telnet Com Port Control Option
• RFC 2941 Telnet Authentication Option
• RFC 2942 Telnet Authentication: Kerberos Version 5
• RFC 2943 TELNET Authentication Using DSA
• RFC 2944 Telnet Authentication: SRP
• RFC 2946 Telnet Data Encryption Option
• RFC 4248 The telnet URI Scheme
• RFC 4777 IBM's iSeries Telnet Enhancements

TELNET clients

Windows

• AbsoluteTelnet is a client for all versions of Windows, and includes telnet, SSH1, and SSH2.
• Hyperterminal Private Edition is another Windows telnet client, free for personal use.
• TeraTerm is a free telnet/SSH client for Windows that offers more features than the built-in telnet as well as offering a free SSH plug-in.
• TN3270 Plus is a telnet/SSH client for Windows.
• Windows comes with a built in telnet client, accessible from the command prompt.

Macintosh

• tn3270 is a free TELNET client for Macintosh designed to work with IBM mainframe systems that use the TN3270 protocol.
• Terminal is a TELNET capable command line interface application that comes as part of all versions of Macintosh OS X.
• NiftyTelnet is a small Telnet client for older MacOS versions that also support SSH.
• dataComet is a full-featured Telnet & SSH application for the Macintosh.

TN3270 Running on a Mac OS X System TN3270 is the remote-login protocol used by software that emulates the IBM 3270 model of mainframe computer terminal. ... Terminal in OPENSTEP. Terminal (also referred to as Terminal. ...

Multiplatform

• PuTTY is a free SSH, TELNET, rlogin, and raw TCP client for Windows, Linux, and Unix.
• mTelnet is a free full-screen TELNET client for Windows & OS/2. Easy to use client with Zmodem download capability.
• Twisted Conch includes a telnet client/server implementation.
• IVT is a free multisession TELNET client for Windows & DOS. Also supports SSH and Kerberos (not free). Includes useful features like auto-login and scripting.
• SyncTERM is a free open-source TELNET/RLogin/SSH client/terminal for Windows and *nix platforms with windowed/full-screen and Zmodem support.

PuTTY is a free software SSH, Telnet, rlogin, and raw TCP client. ... In computing, Secure shell, or SSH, is both a computer program and an associated network protocol designed for logging into and executing commands on a remote computer. ... In computing, rlogin is a Unix software utility that allows users to log in on another host via a network, communicating via TCP port 513. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ... In computing, a client is a system that accesses a (remote) service on another computer by some kind of network. ... Twisted is an event-driven networking framework written in Python and licensed under the MIT licence. ...

Free with Source Code

• dtelnet is a free TELNET client for Windows.
• Pueblo/UE is a free TELNET client for Windows with support for in-line HTML.
• Console telnet is a full screen (console) TELNET client for MS Win32 environments.

Non-free Source Code

• Whitehorn Secure Terminal free TELNET client for Windows.
• Simpterm is a Unicode savy TELNET client for MS Win32 environments that for example can be used for Chinese.
• SimpleMU is a shareware TELNET client.
• CRT and SecureCRT are TELNET clients with scripting capabilities in VBScript, Javascript and Perl.

TELNET servers

Free with Source Code

• telnetd is an embeddable TELNET daemon written in Java.
• Poor Woman's Telnet Server is a standalone java TELNET server which bases upon telnetd.
• Synchronet is a Win32 and Linux BBS Server that also supports http, nntp, pop3, ftp and other protocols.