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000132_news@newsmaster….columbia.edu _Tue May 26 09:54:06 1998.msg
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From: Skip Collins <collibf1@jhuapl.edu>
Newsgroups: comp.protocols.kermit.misc,comp.sys.hp48
Subject: Re: Kermit on the HP48 (Was: One-Way Transfer)
Date: 26 May 1998 08:50:05 -0400
Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
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Xref: news.columbia.edu comp.protocols.kermit.misc:8795 comp.sys.hp48:81461
jhmeyers@miu.edu (John H Meyers) writes:
> Someone:
(otherwise known as Skip Collins)
> : As long as you are cataloging peculiarities, the HP48 sends packet
> : sequence numbers that are larger than 63. One can compensate by doing
> : mod63 before verifying. Is this right?
>
> Frank da Cruz (who wrote the book:)
> > Packet numbers should be 0-63, period. The packet length field
> > is one byte long, and contains a printable character.
>
> Could it be that the original writer did not account for
> "adding 32" to the binary count value? My HP48 transfers files
> requiring hundreds of packets, without problem, so we can
> credit HP with not implementing a completely non-functional Kermit,
> inasmuch as no one has ever reported a file which it could not
> transfer (if it fits in memory).
The hp48 can send invalid sequence numbers. But I had forgotten the
circumstances which can cause the behavior. After searching for my original
post in deja news, I now recall that only error packets have this
problem. I quote the text of that post below.
Skip Collins
---
Quoted from http://www.dejanews.com/getdoc.xp?AN=288295828
This is a small, relatively harmless, but nevertheless real bug in ROM R.
When sending an error packet, the kermit routine may send an invalid
packet sequence number. The sequence number is supposed to be limited to
the range 0 to 63. But when generating an error packet after pressing ON
during a transfer, the packet number may exceed 63. Apparently someone
forgot to do an '& 63' to the internal packet number before generating
the error packet.
I suppose it is possible that a bad character could be sent out, thereby
preventing the error message from being received. Also, some kermit
receivers may timeout waiting for a valid packet to arrive. I discovered
the problem while writing a quick and dirty kermit. My solution was to do
'& 63' on all incoming sequence numbers.
Skip