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From: iwm@doc.ic.ac.uk (Ian Moor)
Newsgroups: mod.computers.vax
Subject: Symbionts
Message-ID: <8605292106.a007681@ivax.doc.ic.ac.uk>
Date: Thu, 29-May-86 16:06:53 EDT
Article-I.D.: ivax.8605292106.a007681
Posted: Thu May 29 16:06:53 1986
Date-Received: Sat, 31-May-86 15:54:52 EDT
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I am trying to produce a symbiont to interface to various machines over
our LAN - an IBM, Unix etc talking various protocols. In all cases I have
programs already running that do the work of the transfer (kermit etc).
The problem is debugging the symbiont - written in Pascal. Symbionts run
with all of SYS$INPUT, SYS$OUTPUT, SYS$ERROR and SYS$COMMAND directed to
JOB_CONTROL, when my symbiont crashes it sends a backtrace to SYS$ERROR,
JOB_COTROL reports the 'unexpected message' BUT DOESNT SAY WHAT IT IS!
and the crashes when it gets an EOF from the symbiont. I have to restart 
all of the queues, and once lost the queue file. I have tried catching
the error using an exception handler, which works sometimes, but would
like to know how to redirect the error messages reliably. Does anybody have
a test harness for symbionts (which is more reliable than JOB_CONTROL!).
--- Well at least the interface is documented in VMS 4.