[nos-bbs] JNOS <-> WL2K forwarding over telpac connection - notes

[Jay Nugent]

Greetings,
   Telnet has been a problem in many ways.  Some telnet servers and
clients fail to properly support "NVT" Network Virtual Terminal, and/or
fail to negotiate the 'proper' terminal settings when the telnet session
is first established.  This has been most prevelent in M$ products.  
More, below...
  

On Tue, 7 Mar 2006, Barry Siegfried wrote:

> Hi, Maiko (et al)...
> 
> > It needs work, more later.
> >
> > > This should also give us telpac if we can handle the various
> > > transparent modes and CR/LF options.
> >
> > That's what I'll have to figure out. The CR/LF options are not a
> > big deal now that I know about the CR only (like early XFBB).
> 
> I don't know if this will help you, but back in the days when I
> was a mere lad, there was a short thread on the old nos-bbs list
> about the JNOS telnet dropping the first character of a line.  I
> don't know much about "telpac" or what its EOL protocol is (I am
> extrapolating by your discussion that it is a CR-only protocol),
> but the following exchange might help you with ASCII-style socket
> EOL translation which always seems to have been difficult to get
> working under <all> circumstances.  If you would like, I can make
> the algorithm and the code available to you which solved this EOL
> translation problem in recvchar().
> 
> Here is the original short thread:
> 
> Date: Wed, 27 May 1998 04:02:29 -0400
> Message-Id: <12141.bgs at k2mf.ampr.org>
> From: "Barry Siegfried" <bgs at k2mf.ampr.org>
> Subject: Re: telnet dropping first character
> 
> [aa5mt at gate.kc5aug.ampr.org wrote]:
> 
> > On some telnets, I drop the first character of every line.
> > On others, all is ok.  I know it's somewhere in my setup.
> 
> It is not.
> 
> > I drop the first character at home and on the bbs using JNOS.  I
> > tried telnetting from ucsd.edu and all is ok to the same site.
> > Where should I begin looking?  It should be an easy fix I would think.
> 
> Actually, it isn't an easy fix, but there is one.  The problem is not
> really with NOS.  What is happening is that you are telneting to a site
> at which the socket code there is not translating its application to use
> the standard internet end-of-line sequence, which is CR-LF, over your
> connection.  The site to which you are telneted is probably marking its
> end-of-lines with only a CR instead.  NOS properly interprets the next
> character received after the first end-of-line character in such cases
> as the second end-of-line character and throws it away, even if it is
> not.
> 
> This is a typical problem at sites where the application you are using
> formerly ran (or simultaneously runs) over a terminal modem connection,
> where the use of only a CR to mark end-of-lines is commonplace.
> 
> Selcuk Ozturk, N3YCO and I worked on this several years ago.  The
> subfunction recvchar() in SOCKUSER.C must be modified to accommodate
> these broken end-of-line sequences from these servers.  It can be done
> but it requires the addition of another variable to the user socket
> structure and some juggling of code inside recvchar().  Note also
> that this change will also affect the "recording" of such sessions
> into a disk file and the subfunction which handles that must also
> be modified to accommodate the changed code in recvchar().
> 
> 73, de Barry, K2MF >>



Per RFC-854:
--------------------------------------------------------
1.  When a TELNET connection is first established, each end is
   assumed to originate and terminate at a "Network Virtual Terminal",
   or NVT.  An NVT is an imaginary device which provides a standard,
   network-wide, intermediate representation of a canonical terminal.
   This eliminates the need for "server" and "user" hosts to keep
   information about the characteristics of each other's terminals and
   terminal handling conventions.  All hosts, both user and server, map
   their local device characteristics and conventions so as to appear to
   be dealing with an NVT over the network, and each can assume a
   similar mapping by the other party.  The NVT is intended to strike a
   balance between being overly restricted (not providing hosts a rich
   enough vocabulary for mapping into their local character sets), and
   being overly inclusive (penalizing users with modest terminals).
-----------------------------------------------------------


   This bites us in the butt every time a MicroShaft user attempts to
telnet over the Internet to a JNOS box.  He either loses the first
character of every line, is required to send TWO CR's at the end of every
line, or has NO echo and has to type in the blind.

   I have always believed this to be a more recent MicroShaft problem, as
it used to work in the Win3.1 and Win95 days, *may* have worked with Win98
as well (my memory is a bit crusty).  But it absolutely FAILS with the
telnet client in WinXP-Pro :-(   The solution has been to use "Putty" 
which DOES properly support NVT and/or negotiate the termial parameters.

   So, to bring this back on topic:  Does the telnet server that WinLink
is using (being M$ based) support NVT and the terminal parameter
negotiation?  Or are they just as buggered up as the rest of the M$ telnet
tools?

   Point is:  You will likely have to code around all the M$ mistakes in
its implementation of TELNET as they obviously never read nor followed the
RFC's.  But hey, they're big, they don't need no stinkin' rules...  
DOH!!!


      --- Jay Nugent  WB8TKL
             
"Getting rid of terrorism is like getting rid of dandruff.  It cannot
 be done completely no matter how hard you try." -- Gore Vidal
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