scott@spectra.com (Tim Scott) (05/25/91)
I have received quite a bit of mail about the "shared X" facilities.
Essentially, I was asking about software that would allow a client to
display simultaneously on more than one display. Note: this is a long
[100-140 lines] posting.
The first place to look is always the monthly FAQ posting. Here it is:
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Subject: 76)* How can I "tee" an X program identically to several displays?
There are several protocol multiplexer tools which provide for the
simultaneous display of X clients on any number of machines.
XMX (an X Protocol Multiplexor) is available from wilma.cs.brown.edu
(128.148.31.66) as pub/xmx.tar.Z
SHX from Michael Altenhofen of Digital Equipment GmbH CEC Karlsruhe
also does this; it is a "WYSIWIS" (What You See Is What I See) package in the
context of a computer-based learning/training tool to provide online help from
remote tutors but is also useful for general window sharing. Information:
shX@nestvx.enet.dec.com. SHX can be found on export and
gatekeeper.dec.com:/pub/X11/contrib/shX.tar.Z,
crl.dec.com:/pub/X11/contrib/shX.tar.Z
XTrap is implemented as a server/library extension. It is available as:
gatekeeper.dec.com pub/X11/contrib/XTrap_v31.tar.Z
export.lcs.mit.edu contrib/XTrap_v31.tar.Z
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Here is some more information about the above applications and others
that I received as responses to my posting. (And from other sources).
1. Shared X (Hewlett-Packard Co.)
Hewlett-Packard Co. has a commercial product, "Shared X" which works under
HP-UX currently on their 300 and 400 series workstations. The product number
is B2305A for the media and manuals ($495) and B2305L for the license.
Pricing for licenses is as follows: qty 1-7 $495 each, 8-user $3300,
24-user $9000, 48 user $15000, 96 user $25000.
They do not recommend more than 4-5 users for CAD/CAM applications. A
version for their 700 and 800 series workstations will be released towards
the end of 1991.
If I understand the analyst I talked to, it works by temporarily replacing
the X server with a special one (saving the original to disk) and restoring
the original when the session is done. This requires 3 MB of disk space
for this swapping.
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2. Shared X (Michael Althenhofen)
This is a modified X library (shXlib) which can be used to provide "naive"
X applications with the capability to work with several displays
simultaneously, dynamically add and remove new displays, and hand input
control from display to display. Since it is a library, you must have
the source of the client to relink. It was part of Herr Altenhofen's diploma
thesis work and was finished about a week before X11R4 was released.
"It may be generally useful for group work and presentations. Currently
there's very little documentation (we are writing a report of the work)
and it surely is somewhat buggy."
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3. xmx (John Bazik)
This is a protocol multiplexor which is independent of the server and does
not affect the application being shared. It was developed at Brown University
for use in their electronic classroom, and (some form of it) has been in use
since 1988. Author John Bazik states: "I'm currently working on version
2, to be released sometime this summer, which will fetch your slippers and
pour you a cup of coffee. It addition to the things listed in the README
file [including support for "late joiners"], it will support "passing the
floor" (allowing another particpant to gain input control."
Cameron Humphries reports: "Basically it pretends to be a server and you
run your application as if xmx was the display. xmx then accepts requests
from the client application and forwards them to all the displays it controls.
It accepts responses from the [paticipating] displays but ignores all but
those from the master display, which then gets sent back to the client.
xmx also has the option of mirroring all mouse movements on all displays
(a bonus in our case). The only downfall occurs if the users who are
supposed to be viewing the demonstration move the window somewhere else...
We combat this by sharing the window manager from the master and this doesn't
allow the users to do anything at all. Probably its other minor bug is that
it doesn't speak Xdmcp so you need to kill xdm on all screens you want
to control first."
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4. X conferencing project (UNC)
jeffay@cs.unc.edu writes me that a group of researchers at UNC have
developed/are in the process of working on a facility "for sharing the output
of an X client among multiple X servers. The result is a system that allows
multiple users to interact with a generic X client. We refer to such multi-
user interactions as a 'conference.' Our system is distinguished by the
fact that we've solved a number of hard/awkward problems that other's
haven't addressed (like the ability to allow remote users to join a
conference already in progress.)
"The system runs under X11R4. We've been using it on Sun-3s, Sun-4s,
DEC 3100s, and the IBM RS/6000."
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5. Unknown
I received some mentions of other possible systems, but I haven't yet
received any information about them. These may not even be X based, but
might be groupware. For your information, here is the list:
XVT feit@cs.odu.edu
Hussein M. Abdel-Wahab, Dept of Comp Sci, Old Dominion Univ.,
Norfolk, VA 23429, USA
Dialogo Lantz and Lauwers [1988], Olivetti Research Center
Shadows John Patterson
Bellcore, 445 South St., Morristown, NJ 07962-1910, USA
Rapport J. R. Ensor
AT&T Bell Labs, Holmdel, NJ 07733, USA
Thanks to:
Cameron Humphries cameron@cs.flinders.oz.au
John Bazik jsb@cs.brown.edu
jeffay@cs.unc.edu
and anyone else who I may have omitted.neideck@kaputt.enet.dec.com (Burkhard Neidecker-Lutz) (05/28/91)
In article <1991May24.170050.25768@spectra.com> scott@spectra.com (Tim Scott) writes: >This is a modified X library (shXlib) which can be used to provide "naive" >X applications with the capability to work with several displays >simultaneously, dynamically add and remove new displays, and hand input >control from display to display. Since it is a library, you must have >the source of the client to relink. You don't need sources, we provide you a protocol bridge. It has been in the files on export.lcs.mit.edu and gatekeeper.dec.com from day one. >4. X conferencing project (UNC) > > Our system is distinguished by the >fact that we've solved a number of hard/awkward problems that other's >haven't addressed (like the ability to allow remote users to join a >conference already in progress.) > >"The system runs under X11R4. We've been using it on Sun-3s, Sun-4s, >DEC 3100s, and the IBM RS/6000." Ahem, shX runs on DECstations, VAXstations , SUN 3's and SUN 4's, has been demoed against AUX servers and is used by folks at IBM. It handles dynamic addition (and deletion) of new users (late comers) can handle multiple conference sets simultaneously and performs a pretty good job in mapping visuals of different kinds between say 1-bit and 8 bit machines. Granted, the version we have internally is somewhat better than what is on USENET. Unlike the HP folks we don't need to change your X server, so it is readily available to anybody on the same network. In fact, the machine that runs the protocol bridge (shXbridge) doesn't have to be a machine with a X display at all (we offer shX as a network service to our VMS machines from a DECStation 5000/200 on the net). >5. Unknown > >I received some mentions of other possible systems, but I haven't yet >received any information about them. These may not even be X based, but >might be groupware. For your information, here is the list: >Dialogo Lantz and Lauwers [1988], Olivetti Research Center > This is a strange one. It was X based but multiplexes by running replicas of the application (!!) on the different machines and then feeds them the same input (sort of what XTrap is about). Get's interesting when they try to replicate the rest of the environment the multiplexed application needs (i.e. two replicas of an editor trying to edit the same file...). Chris Lauwers demoed it to me a few days before the whole Lab was literally nuked by shortsighted management at Olivetti. >Shadows John Patterson > Bellcore, 445 South St., Morristown, NJ 07962-1910, USA He presented this at the 4th annual X technical conference (1990). It didn't handle anything but monochrome and relied on perfect backingstore. Good talk though. Burkhard Neidecker-Lutz (CEC Karlsruhe, Project NESTOR) shx@nestvx.enet.dec.com
abmg@cathedral.cerc.wvu.wvnet.edu (Aliasghar Babadi) (05/28/91)
COMIX is another shared X tool that I developed at West Virginia University (CERC), to share an X based application. Clients can connect to COMIX ( pesudo-sever) which mulicasts the clients' output to other displays and gets the input of each display and passes them to the client, so several users can interact with a single application from their workstations. Regards. Aliasghar Babadi Margha abmg@cerc.wvu.wvnet.edu CERC West Virginia University Drawer 2000 Morgantwon, WV 26506