717:
788:, to issue commands to a server and examine the responses. For example, Telnet client applications can establish an interactive TCP session to a port other than the Telnet server port. However, communication with such ports does not involve the Telnet protocol, because these services merely use a transparent 8-bit TCP connection, because most elements of the telnet protocol were designed around the idea of accessing a
1232:
except 0xff are transmitted over Telnet as is. (0xff, or 255 in decimal, is the IAC byte (Interpret As
Command) which signals that the next byte is a telnet command. The command to insert 0xff into the stream is 0xff, so 0xff must be escaped by doubling it when sending data over the telnet protocol.)
822:
The older protocol is used these days only in rare cases to access decades-old legacy equipment that does not support more modern protocols. For example, a large number of industrial and scientific devices only have Telnet available as a communication option. Some are built with only a standard
838:
Despite recommendation against it, security researchers estimated that 7,096,465 exposed systems on the
Internet continue to use Telnet as of 2021. However, estimates of this number have varied significantly, depending on the number of ports scanned beyond the default TCP port 23.
499:(NCP). The telnet service is best understood in the context of a user with a simple terminal using the local Telnet program (known as the client program) to run a logon session on a remote computer where the user's communications needs are handled by a Telnet server program.
827:
port and use a serial server hardware appliance to provide the translation between the TCP/Telnet data and the RS-232 serial data. In such cases, SSH is not an option unless the interface appliance can be configured for SSH (or is replaced with one supporting SSH).
588:. Telnet services can also be exploited to leak information about the server (such as hostnames, IP addresses and brand) by packet sniffing the banner. This information can then be searched to determine if a Telnet service accepts a connection without
681:(SASL) authentication that address the above concerns. However, most Telnet implementations do not support these extensions; and they do not address other vulnerabilities such as parsing the banner information.
635:
any data sent over the connection (including passwords), and so it is often feasible to eavesdrop on the communications and use the password later for malicious purposes; anybody who has access to a
568:
The Telnet service is the application providing services over the Telnet protocol. Most operating systems provide a service that can be installed or enabled to provide Telnet services to clients.
55:
Telnet consists of two components: (1) the protocol itself which specifies how two parties are to communicate and (2) the software application that provides the service. User data is interspersed
540:
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
91:, one of the first Internet standards. Telnet transmits all information including usernames and passwords in plaintext so it is not recommended for security-sensitive applications such as
740:
on a remote host. 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
488:
23 or 2323, where a Telnet server application is listening. The Telnet protocol abstracts any terminal as a
Network Virtual Terminal (NVT). The client must simulate a NVT using the
1284:) is intended to transmit binary data, not ASCII characters. The standard suggests the interpretation of codes 0000–0176 as ASCII, but does not offer any meaning for high-bit-set
752:(SSH) protocol. 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
1341:
The "Go Ahead" command code (249) in the original Telnet protocol is used to notify to the other end that the other end could start sending back messages. This was used in "
658:
Most Telnet implementations lack authentication. An estimated 22,887 Telnet-enabled devices found by security researchers not only lacked authentication but also provided
651:
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
990:
Telnet commands consist of at least two bytes. The first byte is the IAC escape character (typically byte 255) followed by the byte code for a given command:
2405:
is a BBS terminal program supporting Telnet, SSHv2, RLogin, Serial, Windows, *nix, and Mac OS X platforms, X/Y/ZMODEM and various BBS terminal emulations
1288:
octets. There was an attempt to introduce a switchable character encoding support like HTTP has, but nothing is known about its actual software support.
556:, IETF documents STD 27 through STD 32. Some extensions have been widely implemented and others are proposed standards on the IETF standards track (see
536:
character set. The primary function of a User TELNET, then, is to provide the means by which its users can 'hit' all the keys on that virtual teletype.
3066:
Shimonski, Robert J.; Eaton, Wally; Khan, Umer; Gordienko, Yuri (2002-01-01), Shimonski, Robert J.; Eaton, Wally; Khan, Umer; Gordienko, Yuri (eds.),
596:
due to being improperly configured. In fact, Telnet is targeted by attackers more frequently than other common protocols, especially when compared to
4095:
2495:
Crocker, Stephen D.; Heafner, John F.; Metcalfe, Robert M.; Postel, Jonathan B. (1971). "Function-oriented protocols for the ARPA computer network".
451:
4005:
3815:
3800:
552:
Many extensions were made for Telnet because of its negotiable options protocol architecture. Some of these extensions have been adopted as
211:
52:. It is a protocol for bidirectional 8-bit communications. Its main goal was to connect terminal devices and terminal-oriented processes.
4035:
3939:
3189:
3161:
678:
544:
with the publication of two NIC documents: Telnet
Protocol Specification, NIC 15372, and Telnet Option Specifications, NIC 15373.
627:
recommends that the use of Telnet for remote logins should be discontinued under normal circumstances for the following reasons:
4110:
2818:
2428:
4061:
3861:
3221:
3136:
3087:
2870:
2746:
2711:
2556:
541:
444:
171:
3254:
4085:
301:
296:
266:
512:
Even though Telnet was an ad hoc protocol with no official definition until March 5, 1973, the name actually referred to
126:
2541:
2019 42nd
International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO)
2671:
496:
373:
316:
241:
2980:
2794:
2646:
2512:
609:
474:
383:
353:
469:
Telnet consists of two components: (1) the protocol itself and (2) the service component. The telnet protocol is a
4090:
437:
368:
161:
92:
84:
3954:
186:
176:
2352:
648:
481:
306:
286:
236:
64:
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226:
221:
216:
4105:
4100:
3067:
2385:
403:
363:
231:
3388:
2460:
2408:
telnet.exe command line utility included in default installation of many versions of
Microsoft Windows.
2314:
3854:
3276:
2391:
1345:" communication, as some terminals could send messages and receive messages, but not simultaneously.
666:
4030:
2380:
client version of Telnet, providing similar functionality of telnet to those hosts which are behind
674:
256:
196:
597:
585:
423:
413:
206:
121:
105:
30:
3117:"Identifying SCADA vulnerabilities using passive and active vulnerability assessment techniques"
792:
and none of these options or mechanisms is employed in most other internet service connections.
3979:
3909:
796:
789:
737:
470:
291:
141:
4050:
3213:
Mechanics of user identification and authentication : fundamentals of identity management
2738:
Mechanics of user identification and authentication : fundamentals of identity management
3974:
3185:
2639:
Dot-dash to Dot.Com: How Modern
Telecommunications Evolved from the Telegraph to the Internet
418:
191:
3839:
3810:
2323:
includes a telnet client and server and is installed by default on many Linux distributions.
4115:
3847:
3371:
3046:
3013:
2954:
2921:
2620:
2381:
744:. The usage of Telnet for remote management has declined rapidly, especially on the public
701:
201:
8:
3949:
3870:
773:
477:
1241:
Telnet also has a variety of options that terminals implementing Telnet should support.
3142:
3079:
2876:
2800:
2717:
2562:
2355:
724:
636:
617:
408:
136:
45:
4040:
4025:
4015:
3919:
3227:
3217:
3132:
3083:
2976:
2913:
2880:
2866:
2857:. IMC '21. New York, NY, USA: Association for Computing Machinery. pp. 195–215.
2790:
2752:
2742:
2707:
2667:
2642:
2612:
2566:
2552:
2508:
2455:
2359:
2326:
2306:
2174:
1229:
847:
The technical details of Telnet are defined by a variety of specifications including
553:
336:
112:
56:
37:
33:
3412:
3146:
2804:
2721:
799:
telnet client could make an HTTP request to a web server on TCP port 80 as follows:
756:
authentication, to ensure that the remote computer is actually who it claims to be.
16:
Network protocol for bidirectional communication using a virtual terminal connection
3884:
3777:
3767:
3757:
3747:
3737:
3727:
3710:
3700:
3690:
3673:
3663:
3653:
3643:
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3593:
3583:
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3466:
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3446:
3361:
3331:
3124:
3075:
3036:
3003:
2944:
2903:
2858:
2849:
Srinivasa, Shreyas; Pedersen, Jens Myrup; Vasilomanolakis, Emmanouil (2021-11-02).
2782:
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2500:
2475:
2272:
2163:
2120:
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2033:
2014:
1995:
1976:
1957:
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1919:
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1407:
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1300:
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848:
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76:
68:
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4010:
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3899:
3889:
3246:
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659:
652:
581:
277:
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3731:
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3607:
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3567:
3557:
3547:
3374:
3355:
2548:
2167:
2124:
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2018:
1999:
1980:
1961:
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3049:
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1513:
1494:
1475:
1456:
1411:
1392:
1373:
1336:
1304:
1274:
852:
685:
684:
IBM 5250 or 3270 workstation emulation is supported via custom telnet clients,
640:
624:
589:
521:
327:
80:
3984:
3924:
2786:
99:. Some extensions to Telnet which would provide encryption have been proposed.
95:
of routers. Telnet's use for this purpose has waned significantly in favor of
72:
4074:
3805:
3231:
3128:
2917:
2756:
2703:
2616:
832:
665:
Most Telnet authentication mechanisms are vulnerable to being intercepted by
60:
41:
3115:
Samtani, Sagar; Yu, Shuo; Zhu, Hongyi; Patton, Mark; Chen, Hsinchun (2016).
2862:
2696:
2015 23nd Signal
Processing and Communications Applications Conference (SIU)
2504:
1018:
End of negotiation (or data block) of a sub-service of a protocol mechanism
2470:
2344:
2310:
749:
741:
246:
96:
3211:
3068:"Chapter 11 - Detecting and Performing Security Breaches with Sniffer Pro"
2850:
2736:
2335:
2330:
1342:
708:(also known as OS/400), port 992 is the default port for secured telnet.
689:
644:
577:
529:
485:
67:(TCP). Telnet was developed as secret technology in 1969 beginning with
753:
632:
394:
1168:
Informs other party that this party will not use a protocol mechanism
3366:
3041:
3008:
2949:
2908:
2607:
2396:
2320:
2779:
9th Asia-Pacific
Conference on Communications (IEEE Cat. No.03EX732)
2497:
Proceedings of the May 16-18, 1972, Spring Joint Computer Conference
3121:
2016 IEEE Conference on Intelligence and Security Informatics (ISI)
2450:
2433:
2411:
2402:
2063:
745:
697:
49:
1155:
Informs other party that this party will use a protocol mechanism
1142:
Initiate the negotiation of a sub-service of a protocol mechanism
716:
3301:
2373:
720:
593:
20:
2848:
3944:
2348:
824:
480:
transport. This protocol is used to establish a connection to
357:
150:
130:
3836:
Contains a list of telnet addresses and list of telnet clients
3186:"TCP/IP Ports Required for IBM i Access and Related Functions"
4045:
3929:
3869:
3072:
Sniffer Pro Network Optimization and Troubleshooting Handbook
2377:
2363:
2340:
765:
705:
693:
533:
378:
156:
88:
2494:
3989:
3590:, Requirements for Internet Hosts - Application and Support
3065:
2855:
Proceedings of the 21st ACM Internet Measurement Conference
2664:
Internetworking: Technological Foundations and Applications
2367:
785:
777:
769:
613:
605:
601:
346:
341:
311:
261:
181:
146:
3332:"Telnet | PDF | Networking Standards | Internet Standards"
2819:"Service Name and Transport Protocol Port Number Registry"
704:
encryption, as SSH does not include 5250 emulation. Under
528:
The TELNET protocol is based upon the notion of a virtual
3797:—The official list of assigned option numbers at iana.org
2973:
WHOIS Running the Internet: Protocol, Policy, and Privacy
781:
166:
3697:, The Q Method of Implementing TELNET Option Negotiation
2999:
A User TELNET - Description of an Initial Implementation
3821:
2690:
DaĹź, Resul; Karabade, Abubakar; Tuna, Gurkan (2015).
1194:
Instruct other party to not use a protocol mechanism
2692:"Common network attack types and defense mechanisms"
3801:
Telnet Interactions Described as a Sequence Diagram
3707:, Telnet Environment Option Interoperability Issues
3114:
3816:TELNET: The Mother of All (Application) Protocols
1181:Instruct other party to use a protocol mechanism
524:(NIC 7176) on Telnet makes the connection clear:
4072:
3162:"Zero-day flaw in Solaris allows remote attacks"
2534:
2499:. Association for Computing Machinery: 271–279.
3806:Telnet protocol description, with NVT reference
2689:
2343:and plink command line are a free, open-source
495:Telnet predated UDP/IP and originally ran over
2592:
1081:Request that other party stops sending output
1068:Request that other party ends current process
700:data streams over Telnet generally do support
696:systems. Clients and servers designed to pass
584:sensitive information including passwords and
29:(short for "telecommunications network") is a
3855:
3684:
2775:"Transport layer security protocol in Telnet"
445:
835:operators for providing public information.
59:with Telnet control information in an 8-bit
3640:, Telnet Authentication: Kerberos Version 5
571:
3862:
3848:
3074:, Burlington: Syngress, pp. 513–565,
2661:
2289:Internet Assigned Numbers Authority (n.d.)
736:Historically, Telnet provided access to a
452:
438:
3871:Uniform Resource Identifier (URI) schemes
3365:
3040:
3007:
2948:
2907:
2781:. Vol. 3. pp. 1033–1037 Vol.3.
2606:
592:. Telnet is also frequently exploited by
4096:Internet Protocol based network software
2995:
2662:Meinel, Christoph; Sack, Harald (2013).
858:
715:
679:Simple Authentication and Security Layer
3244:
3209:
2772:
2734:
1223:
4073:
3523:, Telnet Extended Options: List Option
2893:
1207:Sequence Initializer/Escape Character
489:
3843:
3822:"telnet.org—information about telnet"
3527:
3440:
3257:from the original on 21 December 2016
3216:. Boca Raton: Auerbach Publications.
3110:
3108:
3106:
3104:
3061:
3059:
2970:
2844:
2842:
2840:
2838:
2741:. Boca Raton: Auerbach Publications.
2636:
2422:
3308:. SSH Communications Security, Inc.
3159:
2768:
2766:
2685:
2683:
2593:Postel, J.; Reynolds, J. K. (1983).
2588:
2586:
2584:
2582:
2580:
2578:
2576:
2537:"Implementation of NETCONF Protocol"
2530:
2528:
2526:
2524:
842:
3784:, IBM's iSeries Telnet Enhancements
3610:, Telnet Remote Flow Control Option
3269:
2975:(1st ed.). Wiley. p. 25.
2535:Valenčić, D.; Mateljan, V. (2019).
1449:Output Carriage-Return Disposition
723:running under the Microsoft Telnet
13:
3744:, TELNET SUBLIMINAL-MESSAGE Option
3580:, Telnet X Display Location Option
3435:
3324:
3299:
3101:
3056:
2835:
2666:. X.media.publishing. p. 57.
2432:from 1977 has been recreated as a
2429:Star Wars: Episode IV – A New Hope
1487:Output Horizontal Tab Disposition
985:
759:
731:
502:
14:
4127:
3811:Microsoft TechNet:Telnet commands
3788:
3650:, TELNET Authentication Using DSA
3493:, Telnet Suppress Go Ahead Option
3312:from the original on 25 July 2018
2763:
2680:
2655:
2630:
2573:
2521:
2296:
1404:Remote Controlled Trans and Echo
1236:
764:The Telnet client may be used in
563:
557:
3774:, Telnet Com Port Control Option
3080:10.1016/B978-193183657-9/50015-0
2105:Telnet Remote Serial Port (RSP)
1544:Output Vertical Tab Disposition
1353:Approx Message Size Negotiation
36:that provides access to virtual
3670:, Telnet Data Encryption Option
3453:, Telnet Protocol Specification
3405:
3381:
3348:
3293:
3245:Poulsen, Kevin (2 April 2007).
3238:
3203:
3192:from the original on 2016-09-18
3178:
3153:
3023:
3002:. Computer Research Lab, UCSB.
2989:
2964:
2931:
2887:
2595:"Telnet Protocol Specification"
811:GET /path/to/file.html HTTP/1.1
85:Internet Engineering Task Force
3630:, Telnet Authentication Option
3560:, Telnet Terminal Speed Option
3463:, Telnet Option Specifications
2811:
2728:
2488:
1217:J. Postel and Reynolds (1983)
1031:Data packet that does nothing
979:J. Postel and Reynolds (1983)
616:. Common devices targeted are
514:Teletype Over Network Protocol
1:
4111:Unix network-related software
3721:
3570:, Telnet Terminal-Type Option
3540:, Telnet End of Record Option
3302:"History of the SSH Protocol"
3032:TELNET Protocol Specification
2481:
2436:movie served through Telnet.
673:Extensions to Telnet provide
631:Telnet, by default, does not
547:
482:Transmission Control Protocol
464:
65:Transmission Control Protocol
3660:, Telnet Authentication: SRP
3473:, Telnet Binary Transmission
1878:Negotiate About Window Size
1563:Output Linefeed Disposition
1506:Output Formfeed Disposition
1468:Output Horizontal Tab Stops
7:
4086:Application layer protocols
3734:, Telnet 3270 Regime Option
3620:, Telnet Environment Option
3550:, Telnet Window Size Option
3513:, Telnet Timing Mark Option
3413:"The Lost Worlds of Telnet"
3160:Kirk, Jeremy (2007-02-12).
2549:10.23919/MIPRO.2019.8756925
2439:
2136:Telnet Suppress Local Echo
1783:TACACS User Identification
831:Telnet is commonly used by
492:when messaging the server.
10:
4132:
3685:Informational/experimental
3247:"Telnet, dead at 35...RIP"
3210:Todorov, Dobromir (2007).
2996:J. White (9 August 1971).
2735:Todorov, Dobromir (2007).
2461:List of terminal emulators
1136:SB (Subnegotiation begin)
618:Internet of things devices
578:network-based cyberattacks
507:
18:
4059:
3998:
3877:
2896:"NCP/TCP transition plan"
2787:10.1109/APCC.2003.1274255
2641:. Springer. p. 132.
2392:RUMBA (Terminal Emulator)
2284:
1821:Terminal Location Number
1525:Output Vertical Tabstops
1439:NIC 20197 of August 1978
1426:NIC 20196 of August 1978
1280:The 8-bit mode (so named
1213:
975:
768:network services such as
667:Man-in-the-middle attacks
87:(IETF) Internet Standard
63:data connection over the
3600:, Telnet Linemode Option
3129:10.1109/ISI.2016.7745438
2971:Bruen, Garth O. (2015).
2704:10.1109/SIU.2015.7130435
2245:TELOPT PRAGMA HEARTBEAT
2117:Com Port Control Option
1012:SE (Subnegotiation end)
801:
675:Transport Layer Security
576:Telnet is vulnerable to
572:Security vulnerabilities
497:Network Control Protocol
19:Not to be confused with
4091:History of the Internet
3754:, 5250 Telnet Interface
3717:, TELNET CHARSET Option
3680:, The telnet URI Scheme
2863:10.1145/3487552.3487833
2505:10.1145/1478873.1478908
2305:is a telnet client for
2030:New Environment Option
711:
106:Internet protocol suite
3503:, Telnet Status Option
2773:Mahmood, H.B. (2003).
2698:. pp. 2658–2661.
2637:Wheen, Andrew (2011).
2399:from Van Dyke Software
2269:Extended-Options-List
1992:Authentication Option
790:command line interface
738:command-line interface
728:
620:, routers and modems.
538:
471:client-server protocol
83:, and standardized as
3764:, TN3270 Enhancements
3357:TELNET CHARSET Option
2900:Network Working Group
2599:Network Working Group
859:USASCII control codes
814:Host: www.example.com
806:telnetwww.example.com
719:
526:
3483:, Telnet Echo Option
2543:. pp. 421–430.
2309:. It also supports
2221:TELOPT PRAGMA LOGON
1916:Remote Flow Control
1639:Data Entry Terminal
1267:Binary Transmission
1224:Interpret As Command
532:, employing a 7-bit
34:application protocol
2894:Postel, J. (1981).
1973:Environment Option
1954:X Display Location
1840:Telnet 3270 Regime
1246:
1025:NOP (No operation)
994:
677:(TLS) security and
660:unrestricted access
478:connection-oriented
46:local area networks
4106:Internet Standards
4101:Internet protocols
3528:Proposed Standards
3441:Internet Standards
3123:. pp. 25–30.
2423:In popular culture
2233:TELOPT SSPI LOGON
2011:Encryption Option
1423:Output Line Width
1356:NIC 15393 of 1973
1329:Suppress Go Ahead
1319:NIC 15391 of 1973
1244:
1062:Interrupt Process
993:
748:, in favor of the
729:
554:Internet standards
4068:
4067:
4031:irc / irc6 / ircs
3223:978-1-4200-5220-6
3138:978-1-5090-3865-7
3089:978-1-931836-57-9
2943:. April 3, 1972.
2872:978-1-4503-9129-0
2748:978-1-4200-5220-6
2713:978-1-4673-7386-9
2558:978-953-233-098-4
2329:, a command line
2327:Line Mode Browser
2294:
2293:
2177:
2175:Kermit (protocol)
2148:Telnet Start TLS
2066:
1436:Output Page Size
1221:
1220:
983:
982:
843:Technical details
817:Connection: close
462:
461:
113:Application layer
93:remote management
4123:
3864:
3857:
3850:
3841:
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3833:
3832:
3429:
3428:
3426:
3424:
3409:
3403:
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3400:
3399:
3389:"Telnet Options"
3385:
3379:
3378:
3369:
3367:10.17487/RFC2066
3352:
3346:
3345:
3343:
3342:
3328:
3322:
3321:
3319:
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3297:
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3042:10.17487/RFC0495
3027:
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3011:
3009:10.17487/RFC0206
2993:
2987:
2986:
2968:
2962:
2961:
2952:
2950:10.17487/RFC0318
2935:
2929:
2928:
2911:
2909:10.17487/RFC0801
2891:
2885:
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2846:
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2815:
2809:
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2770:
2761:
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2687:
2678:
2677:
2659:
2653:
2652:
2634:
2628:
2627:
2610:
2608:10.17487/RFC0854
2590:
2571:
2570:
2532:
2519:
2518:
2492:
2476:Virtual terminal
2172:
2061:
1289:
1247:
1243:
1100:Erase character
995:
992:
904:Carriage return
863:
862:
818:
815:
812:
809:
805:
454:
447:
440:
102:
101:
4131:
4130:
4126:
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3994:
3873:
3868:
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3791:
3724:
3687:
3530:
3443:
3438:
3436:Further reading
3433:
3432:
3422:
3420:
3419:. 10 March 2019
3411:
3410:
3406:
3397:
3395:
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3283:
3281:www.sysadmin.md
3275:
3274:
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3260:
3258:
3243:
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3208:
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3195:
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3188:. IBM Support.
3184:
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3090:
3064:
3057:
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3024:
2994:
2990:
2983:
2969:
2965:
2940:Telnet Protocol
2937:
2936:
2932:
2892:
2888:
2873:
2851:"Open for hire"
2847:
2836:
2827:
2825:
2817:
2816:
2812:
2797:
2771:
2764:
2749:
2733:
2729:
2714:
2688:
2681:
2674:
2660:
2656:
2649:
2635:
2631:
2591:
2574:
2559:
2533:
2522:
2515:
2493:
2489:
2484:
2446:Banner grabbing
2442:
2425:
2299:
2290:
1897:Terminal Speed
1802:Output Marking
1697:
1663:
1582:Extended ASCII
1279:
1245:Telnet Options
1239:
1226:
1088:Are you there?
988:
986:Telnet commands
940:Horizontal tab
861:
845:
820:
819:
816:
813:
810:
807:
803:
795:For example, a
762:
760:Modern day uses
734:
732:Historical uses
714:
653:packet analyzer
582:packet sniffing
574:
566:
550:
510:
505:
503:Telnet Protocol
467:
458:
278:Transport layer
24:
17:
12:
11:
5:
4129:
4119:
4118:
4113:
4108:
4103:
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3866:
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3837:
3818:
3813:
3808:
3803:
3798:
3795:Telnet Options
3790:
3789:External links
3787:
3786:
3785:
3775:
3765:
3755:
3745:
3735:
3723:
3720:
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3404:
3380:
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3323:
3300:Ylonen, Tatu.
3292:
3268:
3253:. p. 24.
3237:
3222:
3202:
3177:
3152:
3137:
3100:
3088:
3055:
3035:. 1 May 1973.
3022:
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2810:
2795:
2762:
2747:
2727:
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2673:978-3642353918
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2572:
2557:
2520:
2513:
2486:
2485:
2483:
2480:
2479:
2478:
2473:
2468:
2466:Reverse telnet
2463:
2458:
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2424:
2421:
2420:
2419:
2414:
2409:
2406:
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2318:
2303:AbsoluteTelnet
2298:
2297:Telnet clients
2295:
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2179:
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2158:
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2110:
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2059:
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2028:
2024:
2023:
2021:
2012:
2009:
2005:
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2002:
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1990:
1986:
1985:
1983:
1974:
1971:
1967:
1966:
1964:
1955:
1952:
1948:
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1796:
1795:
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1784:
1781:
1777:
1776:
1774:
1765:
1764:End of Record
1762:
1758:
1757:
1755:
1746:
1745:Terminal Type
1743:
1739:
1738:
1736:
1727:
1726:Send Location
1724:
1720:
1719:
1717:
1708:
1707:SUPDUP Output
1705:
1701:
1700:
1698:
1696:
1695:
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1291:
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1277:
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1238:
1237:Telnet options
1235:
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1222:
1219:
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1211:
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844:
841:
802:
761:
758:
733:
730:
727:from a router.
713:
710:
671:
670:
663:
662:to the system.
656:
625:SANS Institute
590:authentication
586:fingerprinting
573:
570:
565:
564:Telnet service
562:
549:
546:
509:
506:
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501:
466:
463:
460:
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366:
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349:
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331:
330:
328:Internet layer
324:
323:
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321:
314:
309:
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299:
294:
289:
281:
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159:
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75:, extended in
42:remote systems
15:
9:
6:
4:
3:
2:
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4109:
4107:
4104:
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4097:
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4079:
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4063:
4062:Protocol list
4058:
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3445:
3444:
3418:
3417:The New Stack
3414:
3408:
3394:
3390:
3384:
3376:
3373:
3368:
3363:
3359:
3358:
3351:
3337:
3333:
3327:
3311:
3307:
3306:SSH home page
3303:
3296:
3282:
3278:
3277:"SysAdmin MD"
3272:
3256:
3252:
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3166:Network World
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1316:Reconnection
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1282:binary option
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1075:Abort output
1074:
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974:
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952:Vertical tab
951:
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833:amateur radio
829:
826:
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771:
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479:
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473:, based on a
472:
455:
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90:
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82:
78:
74:
70:
66:
62:
61:byte oriented
58:
53:
51:
47:
43:
39:
35:
32:
31:client/server
28:
22:
3969:
3829:. Retrieved
3825:
3421:. Retrieved
3416:
3407:
3396:. Retrieved
3393:www.iana.org
3392:
3383:
3356:
3350:
3339:. Retrieved
3335:
3326:
3314:. Retrieved
3305:
3295:
3284:. Retrieved
3280:
3271:
3259:. Retrieved
3250:
3240:
3212:
3205:
3194:. Retrieved
3180:
3169:. Retrieved
3165:
3155:
3120:
3093:, retrieved
3071:
3031:
3025:
2998:
2991:
2972:
2966:
2939:
2933:
2899:
2889:
2854:
2826:. Retrieved
2823:www.iana.org
2822:
2813:
2778:
2737:
2730:
2695:
2663:
2657:
2638:
2632:
2598:
2540:
2496:
2490:
2427:
2426:
2417:ZOC Terminal
2286:
1385:Timing Mark
1285:
1281:
1240:
1227:
1214:
1004:Explanation
989:
976:
872:Explanation
846:
837:
830:
821:
797:command line
794:
763:
750:Secure Shell
735:
683:
672:
622:
575:
567:
551:
539:
527:
513:
511:
494:
468:
424:
384:
317:
267:
251:
54:
26:
25:
4116:URI schemes
3980:view-source
2336:NCSA Telnet
2331:web browser
2257:Unassigned
2209:Unassigned
1620:Byte Macro
1343:half duplex
1112:Erase Line
486:port number
4075:Categories
3999:Unofficial
3960:sip / sips
3831:2020-01-07
3826:telnet.org
3722:Other RFCs
3398:2023-01-12
3341:2023-01-12
3286:2023-01-12
3196:2016-09-07
3171:2023-01-12
3095:2023-01-12
2828:2023-01-12
2482:References
2347:, Telnet,
2197:FORWARD_X
1038:Data Mark
1001:Byte code
964:Form feed
928:Backspace
892:Line feed
869:Byte code
754:public key
580:, such as
548:Extensions
465:Components
395:Link layer
3232:263353270
2918:2070-1721
2881:240357287
2757:263353270
2617:2070-1721
2567:195883872
2397:SecureCRT
2321:Inetutils
2185:SEND-URL
1935:Linemode
1228:All data
1124:Go ahead
766:debugging
490:NVT codes
38:terminals
3985:ws / wss
3878:Official
3310:Archived
3255:Archived
3190:Archived
3147:11741873
2805:56798078
2722:11256038
2451:HyTelnet
2440:See also
2434:text art
2412:TeraTerm
2403:SyncTERM
2382:firewall
2254:141-254
2086:CHARSET
2064:IBM 3270
2049:TN3270E
1859:X.3 PAD
746:Internet
698:IBM 5250
530:teletype
475:reliable
50:Internet
3316:14 June
3261:14 June
2374:Rtelnet
2360:Windows
2353:raw TCP
2307:Windows
2287:Source:
2206:50-137
2160:KERMIT
1673:SUPDUP
1601:Logout
1366:Status
1215:Source:
977:Source:
721:BusyBox
649:gateway
633:encrypt
594:malware
516:as the
508:History
425:more...
409:Tunnels
385:more...
318:more...
268:more...
257:TLS/SSL
212:ONC/RPC
149: (
57:in-band
48:or the
21:Telenet
4081:Telnet
4041:magnet
4026:finger
4016:gemini
4006:coffee
3970:telnet
3945:mailto
3920:gopher
3780:
3770:
3760:
3750:
3740:
3730:
3713:
3703:
3693:
3676:
3666:
3656:
3646:
3636:
3626:
3616:
3606:
3596:
3586:
3576:
3566:
3556:
3546:
3536:
3519:
3509:
3499:
3489:
3479:
3469:
3459:
3449:
3423:5 June
3336:Scribd
3230:
3220:
3145:
3135:
3086:
2979:
2916:
2879:
2869:
2803:
2793:
2755:
2745:
2720:
2710:
2670:
2645:
2615:
2565:
2555:
2511:
2456:Kermit
2366:, and
2356:client
2351:, and
2349:rlogin
2275:
2166:
2123:
2092:
2074:XAUTH
2055:
2036:
2017:
1998:
1979:
1960:
1941:
1922:
1903:
1884:
1865:
1846:
1827:
1808:
1789:
1770:
1751:
1732:
1713:
1691:
1682:
1657:
1648:
1626:
1607:
1588:
1569:
1550:
1531:
1512:
1493:
1474:
1455:
1410:
1391:
1372:
1335:
1303:
1273:
1259:Notes
1230:octets
1188:DON'T
1162:WON'T
1050:Break
1007:Notes
875:Notes
851:
825:RS-232
725:Client
692:, and
690:TN3270
686:TN5250
641:switch
637:router
520:
484:(TCP)
252:Telnet
151:HTTP/3
79:
71:
27:Telnet
4051:ymsgr
4046:rsync
4036:ldaps
3930:https
3885:about
3251:Wired
3143:S2CID
2877:S2CID
2801:S2CID
2718:S2CID
2563:S2CID
2378:SOCKS
2376:is a
2364:Linux
2341:PuTTY
1297:Echo
1256:Spec
1253:Name
1250:Code
1149:WILL
998:Name
916:Bell
880:NULL
866:Name
706:IBM i
694:IBM i
558:below
534:ASCII
379:IPsec
157:HTTPS
89:STD 8
4021:feed
4011:ed2k
3990:xmpp
3955:nntp
3940:ldap
3935:info
3925:http
3905:file
3900:data
3895:crid
3890:acct
3782:4777
3772:2217
3762:2355
3752:1205
3742:1097
3732:1041
3715:2066
3705:1571
3695:1143
3678:4248
3668:2946
3658:2944
3648:2943
3638:2942
3628:2941
3618:1572
3608:1372
3598:1184
3588:1123
3578:1096
3568:1091
3558:1079
3548:1073
3425:2022
3375:2066
3318:2017
3263:2017
3228:OCLC
3218:ISBN
3133:ISBN
3084:ISBN
2977:ISBN
2914:ISSN
2867:ISBN
2791:ISBN
2753:OCLC
2743:ISBN
2708:ISBN
2668:ISBN
2643:ISBN
2613:ISSN
2553:ISBN
2509:ISBN
2384:and
2368:Unix
2358:for
2315:SFTP
2313:and
2266:255
2242:140
2230:139
2218:138
2173:See
2168:2840
2125:2217
2094:2066
2062:See
2057:2355
2038:1572
2019:2946
2000:2941
1981:1408
1962:1096
1943:1184
1924:1372
1905:1079
1886:1073
1867:1053
1848:1041
1753:1091
1650:1043
1286:data
1204:255
1201:IAC
1191:254
1178:253
1165:252
1152:251
1139:250
1127:249
1115:248
1103:247
1091:246
1078:245
1065:244
1053:243
1041:242
1028:241
1015:240
786:POP3
778:HTTP
770:SMTP
712:Uses
623:The
614:XMPP
612:and
610:AMQP
606:MQTT
602:CoAP
598:UPnP
560:).
542:UCLA
374:IGMP
354:ICMP
312:QUIC
307:RSVP
302:SCTP
297:DCCP
262:XMPP
242:SNMP
237:SMTP
222:RTSP
197:OSPF
187:NNTP
182:MQTT
177:MGCP
172:LDAP
162:IMAP
147:HTTP
127:DHCP
3975:urn
3965:tag
3950:nfs
3915:geo
3910:ftp
3778:RFC
3768:RFC
3758:RFC
3748:RFC
3738:RFC
3728:RFC
3711:RFC
3701:RFC
3691:RFC
3674:RFC
3664:RFC
3654:RFC
3644:RFC
3634:RFC
3624:RFC
3614:RFC
3604:RFC
3594:RFC
3584:RFC
3574:RFC
3564:RFC
3554:RFC
3544:RFC
3538:885
3534:RFC
3521:861
3517:RFC
3511:860
3507:RFC
3501:859
3497:RFC
3491:858
3487:RFC
3481:857
3477:RFC
3471:856
3467:RFC
3461:855
3457:RFC
3451:854
3447:RFC
3372:RFC
3362:doi
3125:doi
3076:doi
3050:495
3047:RFC
3037:doi
3017:206
3014:RFC
3004:doi
2958:318
2955:RFC
2945:doi
2925:801
2922:RFC
2904:doi
2859:doi
2783:doi
2700:doi
2624:854
2621:RFC
2603:doi
2545:doi
2501:doi
2471:SSH
2386:NAT
2345:SSH
2311:SSH
2277:861
2273:RFC
2194:49
2182:48
2164:RFC
2157:47
2145:46
2133:45
2121:RFC
2114:44
2102:43
2090:RFC
2083:42
2071:41
2053:RFC
2046:40
2034:RFC
2027:39
2015:RFC
2008:38
1996:RFC
1989:37
1977:RFC
1970:36
1958:RFC
1951:35
1939:RFC
1932:34
1920:RFC
1913:33
1901:RFC
1894:32
1882:RFC
1875:31
1863:RFC
1856:30
1844:RFC
1837:29
1829:946
1825:RFC
1818:28
1810:933
1806:RFC
1799:27
1791:927
1787:RFC
1780:26
1772:885
1768:RFC
1761:25
1749:RFC
1742:24
1734:779
1730:RFC
1723:23
1715:749
1711:RFC
1704:22
1693:734
1689:RFC
1684:736
1680:RFC
1670:21
1659:732
1655:RFC
1646:RFC
1636:20
1628:735
1624:RFC
1617:19
1609:727
1605:RFC
1598:18
1590:698
1586:RFC
1579:17
1571:658
1567:RFC
1560:16
1552:657
1548:RFC
1541:15
1533:656
1529:RFC
1522:14
1514:655
1510:RFC
1503:13
1495:654
1491:RFC
1484:12
1476:653
1472:RFC
1465:11
1457:652
1453:RFC
1446:10
1412:726
1408:RFC
1393:860
1389:RFC
1374:859
1370:RFC
1337:858
1333:RFC
1305:857
1301:RFC
1275:856
1271:RFC
1175:DO
967:12
955:11
907:13
895:10
853:854
849:RFC
804:$
784:or
782:FTP
774:IRC
742:SSH
702:SSL
647:or
645:hub
522:206
518:RFC
419:MAC
414:PPP
404:ARP
369:ECN
364:NDP
292:UDP
287:TCP
247:SSH
232:SIP
227:RIP
217:RTP
207:PTP
202:POP
192:NTP
167:IRC
142:FTP
137:DNS
122:BGP
97:SSH
81:855
77:RFC
69:RFC
44:on
40:of
4077::
3824:.
3415:.
3391:.
3370:.
3360:.
3334:.
3304:.
3279:.
3249:.
3226:.
3164:.
3141:.
3131:.
3119:.
3103:^
3082:,
3070:,
3058:^
3045:.
3012:.
2953:.
2920:.
2912:.
2902:.
2898:.
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2853:.
2837:^
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2765:^
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2575:^
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2539:.
2523:^
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1433:9
1420:8
1401:7
1382:6
1363:5
1350:4
1326:3
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1264:0
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931:8
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808:80
780:,
776:,
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643:,
639:,
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600:,
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342:v4
337:IP
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