chaging default port 5900 to port 80
Matthew.van.Eerde "at" hbinc.com
Thu Jun 27 20:24:01 2002
You *cannot* have both the rfb server (5800) and the http server (5900)
listen on the same port. This is a fundamental rule of TCP/IP. Sorry.
Abandon using IE at work for this purpose. Use the client executable.
Download it at work if you have to.
To get the rfb server (which is all you need if you use the client
executable) to listen on port 80, you have to do some math.
The display setting on the *server* needs to be set. The listening port is
always equal to 5800 + the display setting. If the display is 0, the
listening port is 5800. If the display is 36, the listening port is 5836.
If the display is 6000, the listening port is 11836, etc.
The trick is to make the display big enough that the number wraps around
65536 and comes back. So, for your case, I think setting the display to
59816 should work (80 + 65536 - 5800 = 59816). The problem is that
different platforms have a different target number - 65536 on some, 32768 on
The next gotcha is the display you enter on the *client* has to match the
server. Same math applies - you have to enter a large enough number that,
when you add 5800 to it, it wraps around and becomes 80. 59816 should
probably work too.
There are ways you can check. Set the display on your home machine. Then
telnet to address 127.0.0.1 port 80 and see if you get back the RFB
response. If not, try another display number until you can.
From your office machine try telnetting to your home machine port 80. If
you can't then there are other firewall problems besides your office
firewall - probably your home setup or your home ISP. If you can, then try
setting the display number on the vncviewer client executable until you
> -----Original Message-----
> From: Perry, Derek [mailto:PerryD "at" parl.gc.ca]
> Sent: Thursday, June 27, 2002 11:24
> To: 'VNC-List "at" realvnc.com'
> Subject: chaging default port 5900 to port 80
> I've scoured several months' worth archived postings, but I
> can't find the
> answer I need. I have found similar questions, but no valid answer....
> The facts:
> - I have a VNC server running on my home computer (Windows)
> - I am behind a firewall at work
> - I do not administer the firewall
> - Using IE 5.5 to connect from the office, the viewer's java
> applet loads,
> prompting me for a password, and I get the following error
> message when I
> try to login: "java.net.ConnectException: Connection refused"
> The problem:
> - I can't connect to my VNC server from the office because
> the firewall is
> blocking my connection. Outbound TCP port 80 is the only port
> allowed at
> My Questions:
> - Can I change the default port that the VNC server is
> running on? I would
> like to make it run on port 80 instead of the default
> 5800/5900. How can
> this be done?
> VNC-List mailing list
> VNC-List "at" realvnc.com