Talk:Telnet

Encryption
Telnet DOES support encryption. But it has to be negotiated for, and is not on by default (and not all clients and servers support it). But see, for example, http://www.faqs.org/rfcs/rfc2952.html and http://www.faqs.org/rfcs/rfc2953.html

Introduction
There's an incomplete sentence in the introduction. I'd fix it but I don't know what it's supposed to say.


 * "Most network equipment and operating systems with a configuration (including systems based on Windows NT)."

FalsePockets (talk) 01:20, 26 November 2015 (UTC)

Telnet in login
Telnet is used in the login page of many Broadband connections.

Shubhrajit Sadhukhan (talk) 05:20, 17 July 2020 (UTC)


 * As noted below, not really. Telnet operates at the device driver level. The login is generated by the local operating system. This is the service provided on Socket 23, but is not provided by the Telnet protocol. (This is a common misconception. The facts are much more interesting. That most everyone else saw this as an asymmetric terminal to host problem, but Cosell's insight in 1973 was brilliant and unfortunately not something we see often enough. Jeanjour (talk) 19:01, 13 May 2024 (UTC)

Telnet is the name of a protocol + a service + a client
This article mixes the Telnet protocol, Telnet service, and Telnet client.

The Telnet protocol is used to transfer data between the console used and the remote server in both directions. These are e.g. terminal type, width and height of the window. This protocol is used by the telnet client and service, but also by SSH.

On the other hand, only the combination of Telnet service and Telnet client is outdated and insecure, because they transmit the data in plain text. Telnet over an SSH tunnel, on the other hand, is secure. — Preceding unsigned comment added by Lemmi18 (talk • contribs)


 * SSH communicates terminal type as part of the Secure Shell Connection Protocol, not with Telnet. Same for initial window width/height. I think resizes are handled by the terminal emulation itself, not by the encapsulating protocol. Telnet does have an option to communicate that information (what doesn't it have an option for), but I suspect it is done in practice by escape sequences handled by the terminal instead.
 * And I don't think the telnet service (and client combination) is insecure per se. If it provides shell access to a machine, sure, but the telnet service itself is merely a virtual teletype. It could provide text-based amusement services without any security impact, like a public non-secured BBS where anybody could dial in anyway. These can in fact still be found live on the internet.
 * If you think the article can be improved with a clearer separation of which parts of the text apply to protocol, service and client, go ahead. Although I'm having a bit of trouble mentally separating protocol from service. What is the service? The protocol encapsulates a teletype. A common service exposed on that protocol is a Unix shell, but the telnet service is not a Unix shell. Anything goes, your service could be an AAlib live transcoding of your favourite television channel. So what is the telnet service then? You might mention that due to how common it was for some time, people refer to a remote shell as the telnet service, but I think that is not actually what it is, just a common oversimplification based on what it had become by the time it got obsolete. But there was a time before that where it was just the TCP/IP-alternative to your telephone line modem, also something you used to dial in to a BBS rather than a Unix shell. Digital Brains (talk) 10:08, 23 October 2022 (UTC)


 * This is correct that this entry confuses the protocol, service, and client.
 * A subtle but very important point about Telnet that the wikipedia entry gets wrong is that the protocol is symmetrical and not client-server. Telnet is a protocol between terminal device drivers. It is an especially elegant design in how its negotiation works, where commands are also their response and its handling of half- and full-duplex (where it recognizes that a terminal may be half-duplex but the protocol doesn't have to be. Telnet essentially provides a character-oriented IPC facility. Telnet is used by more than one application. Using Telnet on socket 23 is a service that provides terminal access to an operating system. It does not allow a remote user to *control* a computer. At least this article does not claim (as many do) that Telnet is a remote login protocol. It isn't and wasn't intended to be. As stated above, it is a device-driver protocol. Login and any authentication is a function of the destination operating system. 2601:189:4182:A240:B81C:C0F1:D87E:F83D (talk) 13:47, 11 May 2024 (UTC)
 * Had to go back and Login. The above is mine. The source is the Telnet specification and conversations with Bernie Cosell (then of BBN) who came up with the ideas behind the current Telnet. (If interested, I have more detailed text explaining the uniqueness of Telnet and its importance as an elegant solution to several 'oil and water' problems. Something we seldom see anymore. Jeanjour (talk) 13:50, 11 May 2024 (UTC)