[AG-TECH] Weekly SCG Constellation Site Nanocruises

Don Morton morton at cs.umt.edu
Sun Aug 26 11:19:03 CDT 2001


U. Montana will lead this Tuesday's (28 August) SCG Constellation
Site Nanocruise.

Tuesday, August 28
1400 UTC
1000 Jennifer Teig von Hoffman Daylight Time (Eastern)
0900 Argonne/Marty Hoag Daylight Time (Central)
0800 U. Montana / Northwest Territories Daylight Time (Mountain)
0700 Boeing/LLNL/Yukon Daylight Time (Pacific)
0600 Fairbanks Daylight Time (Alaska)

Virtual Venue - Talus

Because I believe we're now all experts in the use of distributed
power point, I'm going to try something new - VNC - Virtual Network
Computing.  This tool allows one to display and/or share desktops
across the Internet.  I don't "think" it's a part of the standard
AG distribution, but I might be wrong.  It's listed under AG software,
and there is an AGDP document on it.  Information and source/binaries
available at


I would recommend that you make sure you have VNC viewer installed on
your display machine before trying this on Tuesday.

I will "serve" a desktop here from our local Beowulf supercomputer.

Thanks to Liam Forbes at Arctic Region Supercomputing Center, I
was recently made aware of a patch to the Unix source for VNC
which allows one to assign two passwords to "vncserver" - a "full-access"
password which allows remote users to share the keyboard and mouse, and
a "display-only" password which will allow remote clients to only "view"
the desktop.  For those who might be interested, the patch is available


The patch is apparently against VNC 3.3.3r1, and the latest source
is VNC 3.3.3r2.  I applied the patch anyway, and it only bombed
in one place, and it was easy enough to make that one change by
hand (simply adding one line to a file) and compile new executables.

However, let me emphasise that if you're only interested in "viewing" remote
desktops, this patch isn't necessary - all you need is "vncviewer."  
Even if you want to "serve" your desktop, you don't "need" this patch,
but without various tricks, remote clients are able to control keyboard
and mouse of YOUR machine.  The Windows vncviewer has an option that
allows users to specify that they only want "display" access, but
as a server, you're "trusting" all other users to do this.  Even
if remote users aren't malicious, they'll often drag their mouse across
their remote display, which messes you up if you're giving a demo.
So, this patch tends to solve such problems, putting access control
in the hands of the server.

When you launch vncviewer, you're asked for a server name / display
number, and a password.  I'll provide the server name / display number
over the mud, and I'll provide the read-only password over the mud.

FYI - VNC is a tool that supplements AG usage.  It wasn't designed for
the AG (in fact, it's been around for a good 5 years now), but can
nicely augment AG sessions.  I've found VNC to be useful off of the
AG, just using it to share desktops across geographically distributed
space along with a telephone call.

See you all on Tuesday!


   Don Morton                      http://www.cs.umt.edu/~morton/
   Department of Computer Science       The University of Montana
   Missoula, MT 59812 | Voice (406) 243-4975 | Fax (406) 243-5139

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