Hi Raphael,

I was using a similar service in my organization for the purpose of
web-based demos (no control of the pc from the remote host).  I was able
to setup VNC with a little bit of creative configuration to perform the
similar function.  With some modifications to what I have done you can
get this to work with control of the remote pc as well.

Basically, I have a linux server acting as the connection point for the
pcs. I start the Xvnc server on the linux host using the following
command:

   # Xvnc -geometry 1024x768 -depth 16 -httpd /usr/local/vnc/classes
-httpport 80 -alwaysshared &

I then start the vncviewer in listen mode to use the virtual display
created by Xvnc:

   # vncviewer -listen -shared -display :0 -viewonly -fullscreen
-geometry 1024x768 -noauto -depth 16 &

On the windows PC that I want to share, I start the VNC Server software
and use the "Add Client Connection" option to connect to the listening
vncviewer on the linux server (port 5500, this is the default).  This
displays the windows desktop on the virtual linux display that was
setup.

The viewing machine then uses (in my case) the Java viewer applet to
access the virtual display on port 80.  You can also use the VNC viewer
software (windows or linux) to connect to this as well.

I have access to the firewall so I can allow port 5500 through.  If you
don't have access to the firewall, you can easily modify the source
(linux vncviewer) to change this default port (no configuration option
to change it to a more common port as far as I can see).

Here's how it works:

Demo Machine --- connects to --> listening vncviewer on linux machine
--> displays information on --> Xvnc Virtual Display <-- receives
connection from -- windows/linux vncviewer or java viewer software.

Hope this helps.

Leonard Leblanc
IT Manager
Emerge - environmental information solutions
Suite 305-250 McDermot Ave.
Winnipeg MB  R3B 0S5
phone: 204.772.7239
fax: 204.775.7946
email: [EMAIL PROTECTED]
website: www.emergeknowledge.com


-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Raphael Zulliger
Sent: Monday, February 16, 2004 8:50 AM
To: [EMAIL PROTECTED]
Subject: customer support with VNC (both PC behind a firewall)

hi!

i recently used netviewer (http://www.netviewer.de). this is a very 
interesting product, that allows other users to access your pc and (if 
allowed) vice versa. also copying files to the "parnter" is rally easy.
BUT the real clue is that this also works if both pc's are behind a 
firewall (at least with most firewalls it seams to work - netviewer 
writes that on their homepage)! I guess (i'm pretty sure) that both pc's

communicate with the netviewer's server. both use the same "registration

number" to enable the netviewer's server to know which partners belong 
to each other...
i haven't sniffed the packets yet and therefore i don't know anything 
about the internals of how they (netviewer) are doing this.

now my question:
    - is there any existing solution that could do something simillar 
(regarding to the firewall-problem) with VNC? (assuming that i have 
access to an internet server where some kind of software may be started)
    - does anyone know how this is done exactly (in details, so it would

be a good starting point to programm such a server myself - or at least 
some keyword for the used technology/method).

please also assume that both partners do NOT have access to their 
firewalls (so port-forwarding is not possible). the firewalls both allow

the pc from the internal network to access the internet by port 80 (and 
doesn't do any wild content scanning to check if the data really is
http).


i'm happy about any hints!

thanks in advance,
raphael

p.s. what i could imagine (but i think it's to easy to be the solution):

a server-program that runs on an internet-server. this app listens on 
port 80 and allows both pc's to connect to it. because the client 
connect, they are allowed to pass the firewall... then the server-app 
just forwards the contents of all packets received from pc1 to pc2 and 
vice versa...
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