Re: TELNET question
William Chops Westfield <billw@cisco.com> Wed, 16 November 1994 03:52 UTC
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Date: Tue, 15 Nov 1994 17:46:59 -0800
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From: William Chops Westfield <billw@cisco.com>
To: Lee Chastain <lee@huachuca-jitcosi.army.mil>
Cc: telnet-ietf@cray.com
Subject: Re: TELNET question
In-Reply-To: Your message of Tue, 15 Nov 94 11:00:03 MST
Message-Id: <CMM.0.90.2.784950419.billw@glare.cisco.com>
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The tester sets up a TELNET server on a non-standard port (2300) for a TELNET USER test. The tester and the IUT are both SUN workstations; the user is operating from a SUN-CMD cmdtool window. I have noticed that when this implementation of TELNET connects to a port other than 23, option negotiation does not take place, and the server (being a tester) does not propose or request any options. Well, this makes the tester pretty broken. A lot of client telnet implementations assume that the server is going to initiate negotiations for most features. If the tester doesn't, it won't test the most commonly used paths... A lot of unix telnets detect when the remote port is NOT the telnet port, and start up the connection with a lot of local handling (line mode, local interrupts, etc.) I'm not sure that the initial settings would be the same in the abscense of telnet negotiations on the normal telnet port or not. The problem arises out of a test for the handling of newlines; if I understand correctly, the default newline under the conditions I've outlined should be the <CR LF>. However, the server sends just the <LF> and the user TELNET Implementation Under Test (IUT) processes it as a newline character. Once again, the tester is broken. Yes, it should be terminating lines with CRLF. However, see below... I know that 0A <LF> is the native newline character for these systems, but are they allowed by the TELNET protocol to default to anything other than <CR LF> ? Here we run into a fundamental question: "When is a telnet connection sending lines?" One can easilly argue that unix, and most other modern computer systems, are not line oriented on their terminal or virtual terminal, but rather character oriented, and therefore telnet should just send a character stream between the client and server (some of those characters will happen to be carriage returns (CR NUL) and Linefeeds (LF), but that's just conincidental, and whether those happen to terminate a semi-mythical "line" is random and indeterminate. However, a server that sends terminal-oriented data with no CRs ("lines" terminated by LF only) is clearly broken, since the chances that this will show up on a remote terminal the same as it would on a local terminal (which is THE GOAL) are very slim (eg here, the client and server are exchanging data in an "internal" format, which is clearly contrary to the spirit of a "network virtual terminal") A server that terminates "lines" with CR NUL LF is perfectly legal, and should work fine. BillW cisco
- TELNET question Lee Chastain
- Re: TELNET question William Chops Westfield
- Re: TELNET question Theodore Ts'o
- Re: TELNET question Lee Chastain
- Re: TELNET question Philippe-Andre Prindeville
- Re: TELNET question William Chops Westfield
- Re: TELNET question Theodore Ts'o
- Re: TELNET question braden
- Re: TELNET question Theodore Ts'o