TELNET
Encyclopedia
Telnet is a network protocol used on the Internet
or local area networks
to provide a bidirectional interactive text-oriented communications 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 system
s with a TCP/IP stack support a Telnet service for remote configuration (including systems based on Windows NT
). Because of security issues with Telnet, its use for this purpose has waned in favor of SSH
.
The term telnet may also 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, login 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 obtain a login prompt to a command line text interface or a character-based full-screen manager.
, 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. 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
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 standard
s, 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)
other people's server
s made encrypted alternatives much more of a necessity.
Experts in computer security
, such as SANS Institute
, recommend that the use of Telnet for remote logins should be discontinued under all normal circumstances, for the following reasons:
These security-related shortcomings have seen the usage of the Telnet protocol drop rapidly, especially on the public Internet
, in favor of the Secure Shell
(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. As has happened with other early Internet protocols, extensions to the Telnet protocol provide Transport Layer Security
(TLS) security and Simple Authentication and Security Layer
(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.
. 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.
Therefore, a Telnet client application may also be used to establish an interactive raw TCP session, and it is commonly believed that such session which does not use the IAC (\377 character, or 255 in decimal) is functionally identical. This is not the case, however, because there are other network virtual terminal (NVT) rules, such as the requirement for a bare carriage return character (CR, ASCII
13) to be followed by a NULL (ASCII 0) character, that distinguish the telnet protocol from raw TCP sessions. On the other hand, many systems now possess true raw TCP clients, such as netcat
or socat on UNIX and PuTTY
on Windows, which also can be used to manually "talk" to other services without specialized client software. Nevertheless, Telnet is still sometimes used in debugging network services such as SMTP, IRC
, HTTP, FTP or POP3 servers, to issue commands to a server and examine the responses, but of all these protocols only FTP really uses Telnet data format.
Another difference of Telnet from a raw TCP session is that Telnet is not 8-bit clean
by default. 8-bit mode may be negotiated, but high-bit-set octets may be garbled until this mode was requested, and it obviously will not be requested in non-Telnet connection. The 8-bit mode (so named binary option) is intended to transmit binary data, not characters though. The standard suggests the interpretation of codes \000–\176 as ASCII, but does not offer any meaning for high-bit-set data octets. There was an attempt to introduce a switchable character encoding support like HTTP has, but nothing is known about its actual software support.
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
or local area networks
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
to provide a bidirectional interactive text-oriented communications facility using a virtual terminal connection. User data is interspersed in-band
In-band signaling
In telecommunications, in-band signaling is the sending of metadata and control information in the same band or channel used for data.-Telephone:...
with Telnet control information in an 8-bit byte oriented
Byte oriented
Byte orientation refers to forms of data processing in which digital data are processed bytewise. For example, communication is called byte oriented or character oriented when the transmitted information is grouped into bytes....
data connection over the Transmission Control Protocol
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
(TCP).
Telnet was developed in 1969 beginning with RFC 15, extended in RFC 854, and standardized as Internet Engineering Task Force
Internet Engineering Task Force
The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...
(IETF) Internet Standard STD 8
STD 8
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....
, one of the first Internet standards.
Historically, Telnet provided access to a command-line interface
Command-line interface
A command-line interface is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks...
(usually, of an operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
) on a remote host. Most network equipment and operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s with a TCP/IP stack support a Telnet service for remote configuration (including systems based on Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
). Because of security issues with Telnet, its use for this purpose has waned in favor of SSH
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
.
The term telnet may also refer to the software that implements the client part of the protocol. Telnet client applications are available for virtually all computer platforms
Platform (computing)
A computing platform includes some sort of hardware architecture and a software framework , where the combination allows software, particularly application software, to run...
. Telnet is also used as a verb
Verb
A verb, from the Latin verbum meaning word, is a word that in syntax conveys an action , or a state of being . In the usual description of English, the basic form, with or without the particle to, is the infinitive...
. 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, login and run the passwd
Passwd (command)
passwd is a tool on most Unix and Unix-like operating systems used to change a user's password. The password entered by the user is run through a key derivation function to create a hashed version of the new password, which is saved...
command." Most often, a user will be telnetting to a Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
server system or a network device (such as a router) and obtain a login prompt to a command line text interface or a character-based full-screen manager.
History and standards
Telnet is a client-server protocolClient-server protocol
In computing, a client-server protocol is a protocol in which there is a single server which listens for connections, usually on a specific port , and one or more clients which connect to it....
, based on a reliable
Reliability (computer networking)
In computer networking, a reliable protocol is one that provides reliability properties with respect to the delivery of data to the intended recipient, as opposed to an unreliable protocol, which does not provide notifications to the sender as to the delivery of transmitted data.A reliable...
connection-oriented
Connection-oriented
Connection-oriented communication is a data communication mode in telecommunications whereby the devices at the end points use a protocol to establish an end-to-end logical or physical connection before any data may be sent. In case of digital transmission, in-order delivery of a bit stream or...
transport. Typically this protocol is used to establish a connection to Transmission Control Protocol
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
(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
Network Control Program
The Network Control Program provided the middle layers of the protocol stack running on host computers of the ARPANET, the predecessor to the modern Internet...
(NCP) protocols.
Before March 5, 1973, Telnet was an ad-hoc protocol with no official definition. 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
University of California, Los Angeles
The University of California, Los Angeles is a public research university located in the Westwood neighborhood of Los Angeles, California, USA. It was founded in 1919 as the "Southern Branch" of the University of California and is the second oldest of the ten campuses...
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 standard
Internet standard
In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force .-Overview:...
s, 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)
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 hackHacker (computer security)
In computer security and everyday language, a hacker is someone who breaks into computers and computer networks. Hackers may be motivated by a multitude of reasons, including profit, protest, or because of the challenge...
other people's server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
s made encrypted alternatives much more of a necessity.
Experts in computer security
Computer security
Computer security is a branch of computer technology known as information security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to...
, such as SANS Institute
SANS Institute
The SANS Institute is a private US company that specializes in internet security training. It was founded in 1989, provides computer security training, professional certification through Global Information Assurance Certification , and a research archive - the SANS Reading Room...
, recommend that the use of Telnet for remote logins should be discontinued under all normal circumstances, for the following reasons:
- Telnet, by default, does not encryptEncryptionIn cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
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, switchNetwork switchA network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
, hub or gateway located on the network between the two hosts where Telnet is being used can intercept the packets passing by and obtain login, password and whatever else is typed with a packet analyzer. - Most implementations of Telnet have no authentication that would ensure communication is carried out between the two desired hostServer (computing)In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
s and not intercepted in the middleMan-in-the-middle attackIn cryptography, the man-in-the-middle attack , bucket-brigade attack, or sometimes Janus attack, is a form of active eavesdropping in which the attacker makes independent connections with the victims and relays messages between them, making them believe that they are talking directly to each other...
. - Commonly used Telnet daemonDaemon (computer software)In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
s 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
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, in favor of the Secure Shell
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
(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. As has happened with other early Internet protocols, extensions to the Telnet protocol provide Transport Layer Security
Transport Layer Security
Transport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...
(TLS) security and Simple Authentication and Security Layer
Simple Authentication and Security Layer
Simple Authentication and Security Layer is a framework for authentication and data security in Internet protocols. It decouples authentication mechanisms from application protocols, in theory allowing any authentication mechanism supported by SASL to be used in any application protocol that uses...
(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.
Telnet 5250
IBM 5250 or 3270 workstation emulation is supported via custom telnet clients, TN5250/TN3270, and IBM serversIBM System i
The IBM System i is IBM's previous generation of midrange computer systems for IBM i users, and was subsequently replaced by the IBM Power Systems in April 2008....
. Clients and servers designed to pass IBM 5250
IBM 5250
IBM 5250 was originally a family of terminal devices sold with the IBM System/34 minicomputer systems. One model was the IBM 5251-11. It also connected to the later System/36, System/38 and AS/400 systems.- Historical origins :...
data streams over Telnet generally do support SSL encryption, as SSH does not include 5250 emulation. Under OS/400
OS/400
IBM i is an EBCDIC based operating system that runs on IBM Power Systems. It is the current evolution of the operating system named i5/OS which was originally named OS/400 when it was introduced with the AS/400 computer system in 1988....
, port 992 is the default port for secured telnet.
Telnet data
All data octets except \377 are transmitted over the TCP transport as is.Therefore, a Telnet client application may also be used to establish an interactive raw TCP session, and it is commonly believed that such session which does not use the IAC (\377 character, or 255 in decimal) is functionally identical. This is not the case, however, because there are other network virtual terminal (NVT) rules, such as the requirement for a bare carriage return character (CR, ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
13) to be followed by a NULL (ASCII 0) character, that distinguish the telnet protocol from raw TCP sessions. On the other hand, many systems now possess true raw TCP clients, such as netcat
Netcat
Netcat is a computer networking service for reading from and writing network connections using TCP or UDP. Netcat is designed to be a dependable “back-end” device that can be used directly or easily driven by other programs and scripts...
or socat on UNIX and PuTTY
PuTTY
PuTTY is a free and open source terminal emulator application which can act as a client for the SSH, Telnet, rlogin, and raw TCP computing protocols and as a serial console client...
on Windows, which also can be used to manually "talk" to other services without specialized client software. Nevertheless, Telnet is still sometimes used in debugging network services such as SMTP, IRC
Internet Relay Chat
Internet Relay Chat is a protocol for real-time Internet text messaging or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file...
, HTTP, FTP or POP3 servers, to issue commands to a server and examine the responses, but of all these protocols only FTP really uses Telnet data format.
Another difference of Telnet from a raw TCP session is that Telnet is not 8-bit clean
8-bit clean
8-bit clean describes a computer system that correctly handles 8-bit character sets, such as the ISO 8859 series and the UTF-8 encoding of Unicode.- History :...
by default. 8-bit mode may be negotiated, but high-bit-set octets may be garbled until this mode was requested, and it obviously will not be requested in non-Telnet connection. The 8-bit mode (so named binary option) is intended to transmit binary data, not characters though. The standard suggests the interpretation of codes \000–\176 as ASCII, but does not offer any meaning for high-bit-set data octets. There was an attempt to introduce a switchable character encoding support like HTTP has, but nothing is known about its actual software support.
Current status
As of mid-2010, the Telnet protocol itself has been mostly superseded for remote login. Telnet is popular in various application areas:- Enterprise networks to access host applications, e.g., on IBMIBMInternational Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
MainframesMainframe computerMainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
. - Administration of network elements, e.g., in configuring routers on a home networkHome networkA home network or home area network is a residential local area network . It is used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices...
, in commissioning, integration and maintenance of core networkCore networkA core network, or network core, is the central part of a telecommunication network that provides various services to customers who are connected by the access network. One of the main functions is to route telephone calls across the PSTN....
elements in mobile communication networks, and many industrial control systemsIndustrial Control SystemsIndustrial control system is a general term that encompasses several types of control systems used in industrial production, including supervisory control and data acquisition systems, distributed control systems , and other smaller control system configurations such as skid-mounted programmable...
. - MUDMUDA MUD , pronounced , is a multiplayer real-time virtual world, with the term usually referring to text-based instances of these. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat...
games played over the Internet, as well as talkerTalkerA talker is a chat system that people use to talk to each other over the Internet. Dating back to the 1980s, they were a predecessor of instant messaging....
s, MUSHMUSHIn multiplayer online games, a MUSH is a text-based online social medium to which multiple users are connected at the same time...
es, MUCKMuckMuck can refer to:*Muck *Muck, Scotland, an island in Scotland*Isle of Muck, a small island connected by sand spit to Portmuck, County Antrim, Northern Ireland*Muck , a number of actions...
s, MOOMOOA MOO is a text-based online virtual reality system to which multiple users are connected at the same time.The term MOO is used in two distinct, but related, senses...
es. - Telnet Bulletin Board SystemsBulletin board systemA Bulletin Board System, or BBS, is a computer system running software that allows users to connect and log in to the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and data, reading news and bulletins, and exchanging...
. - Internet game clubs, like the Internet Chess ClubInternet Chess ClubThe Internet Chess Club is a commercial Internet chess server devoted to the play and discussion of chess and chess variants. ICC currently has over 30,000 subscribing members...
, the Free Internet Chess ServerFree Internet Chess ServerThe Free Internet Chess Server is a volunteer-run Internet chess server. It was organised as a free alternative to the Internet Chess Club , after that site began charging for membership.-History:...
and the Internet Go serverInternet Go serverAn internet Go server is a server that allows players of the game of Go to play against other players online. The two fundamental types of Go server are real-time servers and turn-based servers.- History :...
. - Connection to Amateur RadioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
DX clusters. - Embedded systemEmbedded systemAn embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
s. - Mobile data collection applications where telnet runs over secure networks
Telnet clients
- PuTTYPuTTYPuTTY is a free and open source terminal emulator application which can act as a client for the SSH, Telnet, rlogin, and raw TCP computing protocols and as a serial console client...
is a free, open source SSHSecure ShellSecure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
, Telnet, rloginRloginrlogin is a software utility for Unix-like computer operating systems that allows users to log in on another host via a network, communicating via TCP port 513.It was first distributed as part of the 4.2BSD release....
, and raw TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
clientClient (computing)A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....
for WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, and UnixUnixUnix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
. - AbsoluteTelnetAbsoluteTelnetAbsoluteTelnet is a software terminal client for Windows that implements Telnet, SSH 1 and 2, SFTP, TAPI Dialup and direct COM port connections. It is commercial software, originally released in 1999 and is still in regular development by Brian Pence of Celestial Software.- Features :Some features...
is a telnet client for WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
. It also supports SSHSecure ShellSecure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
and SFTPSSH file transfer protocolIn computing, the SSH File Transfer Protocol is a network protocol that provides file access, file transfer, and file management functionality over any reliable data stream...
, - Host ExplorerHost ExplorerHostExplorer is a terminal emulation programme for the Windows platform currently in version 14 and compatible with Windows7. HostExplorer provides corporations with an easy way of protecting their investment in legacy data while letting them benefit from the latest desktop and web-based...
part of Hummingbird Connectivity; it implements the telnet, TN 3270, 5250, Ansi, and other protocols. - RUMBA (Terminal Emulator)RUMBA (Terminal Emulator)RUMBA is a terminal emulator application which acts as a client for the 3270, 5250, and VT computing protocols. Mainly used to connect to mainframe and various host platforms, terminal emulators like RUMBA connect modern desktop PCs to legacy systems....
- Line Mode Browser, a command line web browserWeb browserA web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
- NCSA TelnetNCSA TelnetNCSA Telnet is an implementation of the TELNET protocol created at the University of Illinois at Urbana-Champaign National Center for Supercomputing Applications in 1986 and continuously developed until 1995...
- TeraTerm
- Passport from Zephyr Corp, available as both regular executables and a web-based SSH/Telnet application
- SecureCRTSecureCRTSecureCRT is a commercial SSH and Telnet client and terminal emulator by VanDyke Software. Originally a Windows product, VanDyke has recently added a Mac OS X version and Linux version .-History:...
from Van Dyke Software - TeSSH from Zugg Software for WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
based upon the zMUDZMUDZugg's MUD Client is a MUD client developed by Zuggsoft. It was first developed in 1995, and was made into shareware in 1996. It supports several enhancements to standard telnet such as the MUD eXtension Protocol , the MUD Client Compression Protocol , MUD Sound Protocol and features advanced...
and CMUD code base also supports SSHSecure ShellSecure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
and SFTPSSH file transfer protocolIn computing, the SSH File Transfer Protocol is a network protocol that provides file access, file transfer, and file management functionality over any reliable data stream... - TN3270 Plus from SDI USA, Inc. available for Windows and supports terminal emulation types TN3270, TN5250, VT100VT100The VT100 is a video terminal that was made by Digital Equipment Corporation . Its detailed attributes became the de facto standard for terminal emulators.-History:...
and VT220VT220The VT220 was a terminal produced by Digital Equipment Corporation from 1983 to 1987.-Hardware:The VT220 improved on the earlier VT100 series of terminals with a redesigned keyboard, much smaller physical packaging, and a much faster microprocessor...
. It also supports SSHSecure ShellSecure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
, TLSTransport Layer SecurityTransport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...
and SSL. - ZOC Terminal
- SyncTERM BBS terminal program supporting Telnet, SSHv2, RLogin, Serial, Windows, *nix, and Mac OS X platforms, X/Y/ZMODEM and various BBS terminal emulations
- PCMan and KKMan are often used by Telnet user in TaiwanTaiwanTaiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, where Telnet BBSBBS-Technologies:* Bulletin Board System, a computer that allows users to dial into the system over a phone line or telnet connection* BIOS Boot Specification, a system firmware specification related initial program load...
are still popular. - PowerTerm InterConnect from Ericom available for Windows, Mac OS XMac OS XMac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, Windows CEWindows CEMicrosoft Windows CE is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows...
and supports 35 terminal emulation types including TN3270, TN5250, VT420VT420The VT420 was a computer terminal designed by Digital Equipment Corporation . Introduced in 1990, it fit up to 50 lines on the screen and supported two sessions, either one through each communication port, or by multiplexing two sessions on one line with a suitable terminal server...
, WyseWyseWyse Technology is an American company that is a leading manufacturer in Cloud Client Computing. Products include thin client hardware and software as well as desktop virtualization. Other products include cloud software-supporting desktop computers, laptops, and mobile devices...
and others with SSH and SSL.
See also
- Virtual terminalVirtual terminalIn open systems, a virtual terminal is an application service that:# Allows host terminals on a multi-user network to interact with other hosts regardless of terminal type and characteristics,...
- Reverse telnetReverse telnetReverse telnet is a specialized application of telnet, where the server side of the connection reads and writes data to a TTY line , rather than providing a command shell to the host device. Typically, reverse telnet is implemented on an embedded device , which has an Ethernet network interface...
- HyTelnetHyTelnet-History: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. It was first developed in 1990 by Peter Scott, then at the University of Saskatchewan in Saskatoon, Canada...
- KermitKermit (protocol)Kermit is a computer file transfer/management protocol and a set of communications software tools primarily used in the early years of personal computing in the 1980s; it provides a consistent approach to file transfer, terminal emulation, script programming, and character set conversion across...
- SSHSecure ShellSecure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
External links
- Telnet Options - The official list of assigned option numbers at iana.org
- Telnet Interactions Described as a Sequence Diagram
- Telnet protocol description, with NVT reference
- Microsoft TechNet:Telnet commands
- Telnet simulation animated
- TELNET: The Mother of All (Application) Protocols