ssh/X tunneling through remote firewall

Alexander Gottwald
Tue Sep 11 01:32:00 GMT 2001

On Mon, 10 Sep 2001, Fred Ramsing wrote:

> This is really a question about ssh rather than about cygwin-xfree
> development, but I'd really appreciate any help.
> I recently installed cygwin-xfree for Window$98.  I can successfully
> connect from the Win98 PC via ssh to my Linux box, but I cannot run
> X-clients under the cygwin-xfree86 X-server when the firewall on the
> remote Linux box is running.  I believe this is because I am not
> implementing X tunnelling properly through ssh.  The X-clients do run
> properly when the remote host firewall is down.  Note that there is no
> firewall on the localhost running cygwin-xfree86.  I am doing a variant of
> the following from an cywin-xfree xterm:
> $> xhost +
> $> ssh login_name@remotehost_ip
> enter password
> $> export DISPLAY=localhost_ip:0.0
> $> xterm &                       # or some other x program
> and I receive the error: Can't open display: localhost_ip:0.0

correct way: 
ssh -X login_name@remotehost_ip
xterm &

ssh sets $DISPLAY to remotehost_ip:10 which is the endpoint of the tunnel.
The other endpoint is on the windowshost and you don't need xhost anymore.

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