Re: RFCS - Telnet commands mixed with 3270 data

[Scott Sminkey - Sustaining Eng Group <[e-mail]>]

Bob Moskowitz wrote:

>I fail to see what
>logic processing it would save the vendors (and thus preformance
>improvements) given that they have to scan for IAC doubling and IAC EORs
>anyway.  But then I don't write code.

Bob, I do write code, tn3270 code in fact! :-) I've been the chief maintainer
for the last couple of years for the tn3270 client implementation that runs
in Xyplex terminal servers.  Given that IAC doubling is a fact of life, and
given that tn3270 and plain telnet implementations are intimately linked
together (consider switching between NVT and tn3270 modes), I don't think that
dealing with IACs embedded in a tn3270 data stream is any big deal. Whether
or not any IAC sequences other than IAC IAC are supported, my code would
still have to figure out what kind of IAC sequence it has received. If it
isn't IAC IAC, chances are the code could just use existing telnet IAC
processing routines with only minor changes. Also, it is quite useful to be
able to use certain IAC sequences, like IAC IP, to emulate real 3270 keys
that don't generate a character code like ATTN (we added this at the request
of a customer whose tn3270 server worked like this). Even if RFCS were to
prohibit only those IAC sequences that have to do with telnet option
negotiation, I'm not convinced that there would be much of an effect on the
design or implementation of client software. I'm much more worried about
having to become SNA fluent and implement all those SNAisms if I have to
implement RFCS. Now that's a lot of work!

- Scott
============
Scott Sminkey                           email: [e-mail]
Software Sustaining Engineering         voice: 508 952-4792
Xyplex, Inc.                            fax: [phone]
295 Foster St.                          (Opinions, comments, etc. are mine,
Littleton, MA 01460                                     not Xyplex's...)