[GLLUG] Red Hat, VNC, and remote displays (was: no subject)

Melson, Paul PMelson at sequoianet.com
Tue Oct 28 16:58:11 EST 2003


I'm afraid I have disagree with you here.  In both cases, you have a
client and a server.  There are some differences in the way that VNC and
X11 handle redraw areas and color, but in the end, the X 'server' or the
VNC client are both just displaying a bitmap on the local machine and
the application being viewed is using resources on the remote machine.

The pro's and con's of each are different.  X11 is much more flexible.
But it's a bandwidth pig, and can have problems with color maps.  VNC is
JAPCAC (just another PC/Anywhere clone), but it's a lot more remote
access-friendly.  It also works with more operating systems.  For
instance, you can view a WinXP desktop via VNC.  Can't do that with X11.
:-)  There's even a WinCE client.  

PaulM

PS - I'd like to shamelessly plug XFree86 for Cygwin.  It rocks.  Remote
apps or not.  I recently got the latest fluxbox-devel to compile along
with a couple of dock-apps.  For those who can't stand WindowMaker (or
can't stand waiting for KDE on Cygwin to load), I highly recommend it,
and would love to help anyone that wants get it up and running.  I would
say that I probably work 30-40% in XFree86 on Cygwin.


PPS - Here is a little tidbit I sent around the office on getting VNC
working w/ XDMCP logins for RedHat 9.  This will look familiar to SuSE
users:

Thought some of you guys might find this useful.  Sorta like Terminal
Services for RedHat, only not. :-)

RedHat package requirements:
xinetd
vnc-server
[ all of the default GNOME/X11 stuff ]


1st, edit /etc/services and add the following line:

vnc-login     5942/tcp     XDM-style login for VNC


2nd, create the file /etc/xinetd.d/vnc and add the following:
service vnc-login
{
        socket_type     = stream
        protocol        = tcp
        wait            = no
        user            = nobody
        server          = /usr/bin/Xvnc
        server_args     = :42 -inetd -once -query localhost -geometry
800x600 -depth 16
        type            = UNLISTED
        port            = 5942
}

5942 was randomly picked just so that it's not 5900-5910 where default
VNC listeners often are.  It has no significance other than it must be
the same here and in /etc/services.


3rd, restart xinetd (`/etc/init.d/xinetd.d restart`)


4th, edit /etc/X11/gdm/gdm.conf

Find the line containing "[xdmcp]" and the line below it:

Enable=false

Change "false" to "true" and save.


5th, restart gdm (`killall -HUP gdm-binary`), but be nice and let the
person at the console log off first.


6th, connect to "hostname:42" using the VNC client of your choice.


It tunnels well via SSH for security, too:

ssh -fN user at linxbox -L 5942:127.0.0.1:5942 && vncviewer localhost:42


Change "-depth 16" to "-depth 8" in /etc/xinetd.d/vnc for slower
connections where 256 colors can do the job.


-----Original Message-----
Thus, the amount of network traffic being generated is highly dependent
on the nature of the application, and X and VNC both generate different
kinds of traffic. Some applications might fare well with X and others
may feel more responsive with VNC. Some might perform horribly on both.
:)


I've always been tempted to try out the Cygwin XFree86 server, but since
my workstation is a FreeBSD machine, I rarely need to display X
applications on a Windows, machine. Much more common is the reverse. :)
Although I'd like to experiment with thin clients running off a central
application server in the near future, so maybe the opportunity will
arise.




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