VNC applet through a proxy connection

My VNC server is behind a proxy (squid) and SmoothWall firewall, I create a port forwarding for 5800 on the firewall to point to my VNC server local net IP.

the client is connected via ISP dialup to open

the first page of VNC is bring up to prompt for password, but after login the applet has exception

What am I missing ? Do I need to forward any other port for this ?
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Joel MillerDevOps EngineerCommented:
Open up 5800-5900. You might be able to get away with less, but initial connections are opened through 5800 and the actual sessions are using ports between 5800-5900.

I suggest opening that whole range for that application.
Joel MillerDevOps EngineerCommented:
BTW - That is what VNC (AT&T) recommends also...
ahTriAuthor Commented:
I can add 10 ports but adding 100 port is quite a night mare, is there anyway to find out which port the server is open ?
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ahTriAuthor Commented:
I add from 5800 to 5809 but no luck
Joel MillerDevOps EngineerCommented:
cant you open a range? That is what they call for...

But this may be what you're looking for...
Joel MillerDevOps EngineerCommented:
Q53 Which TCP/IP ports does VNC use?
A VNC server listens on two ports. The exact port numbers depend on the VNC display number, because a single machine may run multiple servers. The most important one is 59xx, where xx is the display number. The VNC protocol itself runs over this port. So for most PC servers, the port will be 5900, because they use display 0 by default.

In addition, VNC servers normally have a small and very restricted web server built in, which allows you to connect a browser to them and use the Java viewer. This runs on port 58xx. Note that this is the HTTP port used for downloading pages and applets, but once the applet is running it uses 59xx for VNC just like any other viewer.

The servers can be changed to listen on other ports if, for any reason, these are not suitable for you. See the server's documentation for more details. Most of the viewers, if given a display number larger than 99, will interpret it as a direct port number and will not add 5900. See also the next question.

If you are running a viewer in 'listening' mode, where it accepts connections initiated by the server, it will listen for incoming VNC on port 5500.


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See jmiller47's answer and open ports 5900 and 5800 , not the range 5800-5900.

On windowz that's all you need, for linux/unix pen 58xx and 59xx or configure the server to fource the port you want.
ahTriAuthor Commented:
It's work now, I open 5800 and 5900
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