From:	CSBVAX::CSBVAX::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX"  1-MAR-1989 13:46
To:	MRGATE::"ARISIA::EVERHART"
Subj:	TCP/IP support for VMS DECWindows


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Date: 28 Feb 89 23:12:25 GMT
From: quanta.eng.ohio-state.edu!kcgl1.eng.ohio-state.edu!JONESD@tut.cis.ohio-state.edu  (David Jones)
Organization: Ohio State University
Subject: TCP/IP support for VMS DECWindows
Message-Id: <1557@quanta.eng.ohio-state.edu>
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I got a chance last week to play with a VAXStation 3100 at a sales demonstra-
tion and took advantage of the oportunity to investigate how DECWindows was
implemented under VMS.  The sales people were nowhere near as useful as TYPE,
DIRECTORY, and ANALYZE/IMAGE.  Apparently, the DECWindows server is a detached
process running the image DECW$SERVER_MAIN.  All communication between client
applications and the server takes place though a transport layer whose  code
is isolated into a separate shareable image, DECW$TRANSPORT_COMMON.

The DECW$TRANSPORT_COMMON.EXE shareable image defines about 20 routines with
either a DECW$XPORT_ or DECW$$XPORT_ prefix.  There are routines with I/O
sounding names (READ, WRITE, OPEN, CLOSE) and routines that appear to be
memory management oriented (ALLOCMEM, DEALLOCMEM, etc).  To handle the actual
transport protocols, TRANSPORT_COMMON activates additional shareable images
of the form DECW$TRANSPORT_xxxx, where 'xxxx' matches the equivalence names
of the logical name DECW$TRANSPORT_SERVERS.  On the VAXStation I was on,
DECW$TRANSPORT_SERVERS translated to "DECNET","LOCAL".

A TRANSPORT_xxxx image defines one procedure in its global symbol table,
DECW$TRANSPORT_INIT.  This procedure returns the address of a data structure
that contains, among other things, a list of 8 or 9 procedures within the
image.  These procedures in turn call the routines in DECW$TRANSPORT_COMMON.

It looks to me like the hooks are in place to add additional transports
(e.g. TCP/IP, SCS) without any modifications to the existing code.  To link
DECWindows to your own brand of TCP/IP, all we need is the documentation
to the interface.  Has anybody out there seen the documentation that comes
with DECWindows/VMS, and if so, does it mention user-written transports?
(The machines for my site are on order, but I'm impatient to find out).

David L. Jones               |      Phone:    (614) 292-6929
Ohio State Unviversity       |      Internet:
1971 Neil Ave. Rm. 406       |               jonesd@kcgl1.eng.ohio-state.edu
Columbus, OH 43210           |               jones-d@eng.ohio-state.edu

Disclaimer: A repudiation of a claim.