Can't open display: hostname:0.0

[Nigel Wade]

Dave Martini wrote:
> # xclock
> Error: Can't open display: raider4:0.0
> 
> What will cause the above error? I'm logged into a remote machine from 
> my own RHEL 4 box.
> I also typed xhost +hostname from my RHEL 4 box to allow the other 
> machine to display on my server. My DISPLAY environment variable is the 
> correct name of my RHEL 4 box.
> 
> Thank You.
> Dave Martini
> 

Unless you've reconfigured your X startup the X server won't be 
listening for network connections. The X server normally listens on a 
UNIX domain socket (i.e. accessible to the localhost only via the 
filesystem).

The simplest solution is to tunnel the X connection via ssh. Login to 
the remote machine using ssh -Y. This should setup the appropriate 
tunnel for X back to your local display. DON'T modify DISPLAY on the 
remote end.

If you really want to use a direct connection you'll need to modify the 
file /etc/X11/gdm/gdm.conf and set DisallowTCP=false. Then restart X. 
This will enable the X server to receive network connections. You will 
also need to make a hole in the firewall to allow connections to the X 
server port (6000 IIRC).

-- 
Nigel Wade, System Administrator, Space Plasma Physics Group,
             University of Leicester, Leicester, LE1 7RH, UK
E-mail :    nmw at ion.le.ac.uk
Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555