[Simh] Question on telnet mantra in simh

Dave dave.g4ugm at gmail.com
Sun Nov 14 16:59:16 EST 2010



> -----Original Message-----
> From: simh-bounces at trailing-edge.com 
> [mailto:simh-bounces at trailing-edge.com] On Behalf Of J. David Bryan
> Sent: 14 November 2010 21:07
> To: SIMH List
> Subject: Re: [Simh] Question on telnet mantra in simh
> 
> 
> Holger,
> 
> 
> On Thursday, November 11, 2010 at 21:08, Holger Veit wrote:
> 
> > I see: here be dragons.
> 
> Indeed.
> 
> 
> > As a non-native speaker, I have problems figuring out what was 
> > actually intended in RFC854/5 with the WILL/WONT and 
> DO/DONT pairs...
> 
> It is not much easier for this native speaker!  ;-)
> 
> If I read RFC 854 and RFC 1143 correctly, the basic idea is:
> 
>  1. Each side starts with the same known, basic 
> configuration: the Network
>     Virtual Terminal (NVT).
> 
>  2. One side may offer to the other side to enable an option 
> with WILL. 
>     The other side responds with DO if the offer is accepted and DON'T
>     if the offer is rejected.
> 
>  3. One side may request that the other side enable an option with DO.
>     The other side responds with WILL if the request is accepted and
>     WON'T if the request is rejected.
> 
>  4. One side may announce to the other side that it will 
> disable a current
>     option with WON'T.  The other side must acknowledge the 
> announcement
>     with DON'T.
> 
>  5. One side may demand that the other side disable a current 
> option with
>     DON'T.  The other side must acknowledge the demand with WON'T.
> 
>  6. Neither side announces the mode it is in.  Only changes 
> of mode are
>     negotiated.
> 
>  7. If a side receives a request to enter a mode it is already in, the
>     request is ignored.
> 
> 
> > ...and it seems to me that whatever the correct intention 
> was, simh is 
> > broken anyway, beyond incompletely implementing the IAC options 
> > negotiation.
> 
> Correct.
> 
> 
> > In contrast to my idea of having simh report to the client what it 
> > does
> > not like (in contrast to your #2.) simh should only tell 
> what it offers 
> > to handle, so WILL ECHO, WILL BIN, and WILL SGA appears to 
> be okay, but 
> > WILL LINEMODE is not, because simh neither wants to do LINEMODE 
> > suboption negotiation at all nor can it do it at all, so it 
> shouldn't 
> > announce it.
> 
> Correct.
> 
> 
> > However, if the other side would request DO LINEMODE it 
> should deny it 
> > with WONT LINEMODE. The other side is a client, though, so 
> should not 
> > DO LINEMODE at all, according to RFC1184...
> 
> Correct.
> 
> 
> > For the WILL ECHO/BIN/SGA offers, simh should accordingly react 
> > properly when the other side does not accept the offer. 
> While a WONT 
> > BIN from the client seems to be handled correctly, DO/DONT 
> BIN is not, 
> > and the RFC default mode ASCII is not respected. Neither does it 
> > respect a WONT ECHO reply to the DO ECHO it demands.
> 
> Correct.
> 
> 
> > Now, I am curious why this line is present at all.
> 
> Arthur Krewat wrote the following to me in 2007, when I asked 
> that same 
> question:
> 
>   "Most likely because it was easier to hack something together that
>    worked. Some clients needed those to be offered or they'd puke - I
>    think they locked up in negotiation and never fully connected.
> 
>   "Solaris telnet worked with it just fine."
> 
> 
> > Has there been any client relying on this, or do all 
> present clients 
> > deny this offer (which will then be dropped by simh as it 
> ignores what 
> > it does not understand)?
> 
> The four clients that I use respond to SIMH negotiation as follows:
> 
>   Telnet client         Negotiation
>   ====================  
> ================================================
>   Microsoft Telnet      DONT LINEMODE, DO SGA, DO ECHO, DO 
> BIN, WILL BIN

It should be noted that Windows/2000 telnet behaves differently to
Windows/XP Telnet as I know from my experiences with Hercules which for a
time worked with w2k telnet and not with XP telnet... 

>   Microsoft Hyperterm   DONT LINEMODE, DO SGA, DO ECHO, DO 
> BIN, WILL BIN
>   Attachmate Crosstalk  DONT LINEMODE, DO SGA, DO ECHO, DO BIN
>   AICS QCTERM           DO ECHO, DO SUPPRESS LOCAL ECHO, WONT BIN
> 
>                                       -- Dave
> 
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