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000241_news@newsmaster….columbia.edu _Tue Aug 26 19:06:31 1997.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc,comp.unix.questions,comp.unix.admin,comp.unix.misc,comp.unix.ultrix,comp.unix.shell
Subject: Re: Do not get connected at 33.6K
Date: 26 Aug 1997 23:06:27 GMT
Organization: Columbia University
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Message-ID: <5tvnhj$4rh$1@apakabar.cc.columbia.edu>
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In article <5tv6kp$7n9@newslink.runet.edu>,
I l y a <ibeloozePLEASE_REMOVE_THIS_TO_REPLY@runet.edu> wrote:
: Frank da Cruz (fdc@watsun.cc.columbia.edu) wrote:
: : You can only tell C-Kermit to set speeds that are supported by the
: : underlying operating system. 33600 is not such a speed. Use 38400 or
: : 57600 or 76800 or 115200. Read the "Using C-Kermit" manual about speed
: : buffering, flow control, error correction, and compression -- the
: : difference between modulation speed and interface speed, and their
: : reconciliation, is a fundamental aspect of modern modem communications,
:
: Thanks, it was exactly what I was looking. I did not realize that tty
: speed was not the same as modem speed.
:
See Appendix II, "A Condensed Guide to Serial Communications", pages 488-492.
There are also other sections about this at appropriate places, e.g. "Speed
and Flow Control in the Full Duplex Environment", pp.210-212. Also look at
"More About Communication Speeds" on page 60.
: : ... and is covered in depth in Appendix II of the manual:
: :
: : http://www.columbia.edu/kermit/ck60manual.html
:
: Thanks, but it is not a valid URL.at least lynx tells me so.
:
It's there, really.
: I got connected at 38400 but now I
: have a different problem - the screen is messed up and I have been
: trouble shooting it by reseting TERM, cols, rows variables but nothing
: seems to work. elm, tin and other shell programs use only 30 lines or so,
: and even that is messed up. resize and refresing (control-l) does not
: help. I did not have this problem at slower speeds.
:
Then it's probably a lack of effective flow control. If you are using
C-Kermit 6.0, and you give it a "set modem type xxx" command (where xxx is
the kind of modem you have), and if it is a modern error-correcting, data-
compressing, speed-buffering modem (as yours is), AND if your operating
systems supports it, then C-Kermit automatically sets the serial port driver
for RTS/CTS (hardware) flow control and also ensures that your modem is set
for RTS/CTS too. You can also explicitly issue the "set flow rts/cts"
command (but then you also must ensure that your modem is configured
accordingly).
Having said all that, however, I have to tell you that Ultrix does not support
RTS/CTS flow control. But (again, as explained in the manual) when using
speed buffering you MUST have an effective means of flow control BETWEEN THE
COMPUTER AND THE MODEM -- as opposed to end-to-end. Your only choice (unless
somebody else knows something about Ultrix that I don't know) would appear to
be Xon/Xoff "software" flow control. Of course, this prevents you from using
Xon (Ctrl-Q) and Xoff (Ctrl-S) as data characters on your connection. To
set this up with C-Kermit 6.0:
set modem type ppi ; your modem type
set line /dev/tty00 ; your communication device
set speed 38400 ; highest speed offered by Ultrix
set flow xon/xoff ; flow control to be used by Ultrix
prior to dialing. Giving the "set flow" command after the "set modem
type" command overrides any mistakes that Kermit might make (hopefully
none!) in choosing the appropriate flow control for this particular
combination of platform and modem.
Again, it's all explained in the manual.
- Frank