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000208_news@columbia.edu_Thu Jan 19 14:36:12 1995.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: "Can't read character: I/O error"
Date: 19 Jan 1995 14:36:12 GMT
Organization: Columbia University
Lines: 55
Message-Id: <3fltcs$eb0@apakabar.cc.columbia.edu>
References: <3fkupt$3t6@spool.cs.wisc.edu>
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In article <3fkupt$3t6@spool.cs.wisc.edu>,
David Finton <finton@homer.cs.wisc.edu> wrote:
>I've built Kermit5a188 on my NeXTstation. It seems to work okay,
>but it seems to drop the connection often, after giving me the
>message
>
>Can't read character: I/O error
> Communications disconnect (Back at localhost)
>C-Kermit>
>
>What is the cause of this error? Do I have some parameters set
>wrong? I've set flow to none, but was told that I should do this
>because the NeXT does flow control with the port drivers, as long
>as I'm using /dev/cufa, have flow control enabled on the modem, and
>am using the NeXT modem cable (which I am).
>
The current version of C-Kermit is 5A(190), but that will not
necessarily affect this problem. However, the release notes for
version 5A(190) contain more information and are organized better
than in previous releases. In particular, the ckuker.bwr file
(C-Kermit, Unix version "beware" file) contains sections for each
platform. Here are the pertinent excerpts from the section on the
NeXT:
(3.4) C-KERMIT AND NEXTSTEP
The SET CARRIER command has no effect on the NeXT -- this is a
limitation of the tty device drivers.
Hardware flow control on the NeXT is selected not by "set flow
rts/cts" in Kermit (since NeXTSTEP offers no API for this), but
rather, by using a specially-named driver for the serial device:
/dev/cufa instead /dev/cua; /dev/cufb instead of /dev/cub. This is
available only on 68040-based NeXT models (the situation for Intel
NeXTSTEP implementations is unknown).
NeXT-built 68030 and 68040 models have different kinds of serial
interfaces; the 68030 has a Macintosh-like RS-422 interface, which
lacks RTS and CTS signals; the 68040 has an RS-423 (RS-232
compatible) interface, which supports the commonly-used modem
signals. WARNING: the connectors look exactly the same, but the
pins are used in completely DIFFERENT ways -- different cables are
required for the two kinds of interfaces.
IF YOU GET LOTS OF RETRANSMISSIONS during file transfer, even when
using a /dev/cuf* device and the modem is correctly configured for
RTS/CTS flow control, YOU PROBABLY HAVE THE WRONG KIND OF CABLE.
Does this help?
By the way, until it died recently, I had a NeXTstation on my desk,
so I can personally veryify that Kermit works fine on it with the
right kind of cable.
- Frank