Question about linemode implementation...

Steve Parker <> Tue, 26 April 1994 17:52 UTC

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Subject: Question about linemode implementation...
Date: Tue, 26 Apr 1994 10:43:00 -0700
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From: Steve Parker <>
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In rfc1184 there is this text:

+    Normally, the entire user interface is left up to the implementor.
+    However, there is functionality that the user should be able to
+    specify on the client side of the connection.  During a Telnet
+    session, the client side should allow some mechanism for the user to
+    give commands to the local Telnet process.  These commands should at
+    least allow the user to:

+       1)  Change the mode of the connection.  The user should be able to
+           attempt to turn EDIT, FLOW, TRAPSIG, and ECHO on and off.  The
+           server may refuse to change the state of the EDIT and TRAPSIG
+           bits.

My question is about the last sentence above.  I certainly can see how
it is good to require clients to attempt to negotiate these options
when the user requests.  However, nowhere does this make clear when and
why a server might refuse these state changes.  

To me, it seems clear that the server would refuse to negotiate those
options if they were in conflict with the present state of the "pty"
set by the application.  For example, if the application has set the
pty into "raw" mode, negotiating remote edit should probably be refused.
(And I think I can make similar arguments about flow, trapsig and echo.)

Is it correct that a reasonable and compliant linemode server would
refuse mode changes in that way?