Re: TELNET question Fri, 18 November 1994 20:25 UTC

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Date: Fri, 18 Nov 1994 12:12:43 -0800
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Subject: Re: TELNET question
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  *>    The question boils down to this:  Is a TELNET user only a proper implementation
  *>    of TELNET when the server port is 23?         ^^^^
  *> You mean "client" where you wrote "user", right?

Just to keep the record straight, the Telnet protocol was designed in
the early ARPAnet years when the terms "user" and "server" were in use;
I don't think that the term "client" had been invented yet.  The
preferred terminology is "User Telnet implementation" [RFC-1123],
although if you look back over the past 20 years of email discussion of
Telnet, you will find lots of usage of the more informal but ambiguous
term "Telnet user".

  *> That's really the crux of the matter.  The RFC's document the telnet
  *> *protocol*.  The question is when is the client obligated to follow the
  *> telnet protocol, and when is it not so obligated?
  *>    The consequences are as follows:
  *>    1.  No - TELNET is TELNET regardless of the server port :
  *>        Then any implementation which defaults to LF as a newline (such as
  *>        unix-based hosts) is not conformant to the TELNET standard.
  *>        (Possible interoperability problems).
  *>    2.  Yes - TELNET is only TELNET when the server port is 23:
  *>        Not only did the tester send the wrong character(s), but its testing
  *>        methodology is seriously flawed; the use of the non-standard port
  *>        means that it is not truly testing TELNET, whether it had sent the
  *>        correct newline code or not.
  *> Give that the IANA has specified that the port for telnet service is 23,
  *> I would tend towards option 2.  The fair way to test things is on the
  *> original port.
  *> I think it is a "local matter" what the telnet client does going to
  *> other ports.  Ideally, there should be a switch that indicates where or
  *> not the client should be initiating the options negotiations.  How that
  *> switch is offered ought to be presented to the user is a UI issue, and
  *> not one that should be addressed in a protocol specification.  (And,
  *> indeed, there is such a switch on the Berkeley reference implementation;
  *> you simply prefix the port number that you specify with a '-'
  *> character.)
  *> 						- Ted

Both FTP and SMTP both use "telnet streams", with CRLF as end of line.
I would expect that 1. was the right answer, as a question of philosophy.
Of course, reality sometimes intervenes...

Bob Braden