Wagner Lipnharski wrote:

> What Miguel wants is a simple 1k program

  Sadly, very few apps are written in Assembler anymore.  In fact, only
the good ones...  ;-)

> that send broadcasting packets copying the VGA buffer from one
> particular machine.

  As Bill W mentions, this is *not* the way to go.  An approximation
would be to send *changes* to the video buffer, compressed at least
using Run Length Encoding, which used to be the "neat" way to do this
exact task on text screens, but even that is impractical on a 8- or 16-
bit graphics screen at 1024 x 768 which are 786,432 or 1,572,864 bytes
respectively (*that's* why you can't run with less than 2M video
memory).

  What you actually have to do is to "play Windows".  Windows paints the
screen by means of a stream of API calls, only *some* of which contain
block data for graphics.  The trick is to send not screen data, but the
API calls which painted the screen on the sending computer in the first
place.

  As has been mentioned, while this can be patched into M$ Windoze, it
is the *native* structure of the X-server which makes no a priori
expectations about whether the "terminal" (screen & keyboard) are in
fact the local machine, and will just as happily connect, or tee, over
whatever network structure is present.

  Clients such as Xwin32 and M$Win X-servers are available to run on
Windoze.  Not that this helps the current concern.

>  It could be distributed via Ethernet or by a simple 3 wires cable
> (RS485).  The viewers would be using the receiver part of the same
> program, and simply displaying this data.  By programming point of
> view, this is a very, very simple program.

  As noted, it isn't *quite* that simple.  Such things never are.  And
Ethernet and RS-485 are very different bandwidths.  The "raw" sending
proposal is fairly viable over Ethernet.

  (Aside: My present interest is in transmitting a presentation,
presently done using Power Point, down the length of a church hall so
that the control of the presentation is with the "sound crew",
effectively the audio-visual presentation manager nowadays, and the
video projector is fed by a slave PC at the front.

  This may sound turned-about, but it's quite a big hall and the video
projector is quite challenged to provide a bright picture already.  My
base proposal is Ethernet via twisted pair.  I'm wondering whether it
may be practical to run an app on the "master" which interprets the
display into X-server code and have the slave run an efficient Linux
X-system on a turnkey 386 or 486.)

> By the way, for long distance audio conversations I tested Netmeeting
> (Microsoft), to lazy, to heavy, to slow, tested also Iphone5.0
> (Vocaltec), but Iphone4.5 ($50 license) is much faster and reliable.
> Ended up using MediaRing (SoundBlaster), much better sound quality and
> it is free.

  What about Speak Freely?
--
  Cheers,
        Paul B.