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georgeston
15-Mar-2016, 20:13
How do I enable X Windows over telnet?

I realize that is is not secure and one should use ssh; but, we are on a closed intranet and my clients only have access to telnet.

Users can connect using telnet, but when trying to run an X application, get "Error: Can't open display", even though the DISPLAY environment variable is correctly set.

I set DISPLAYMANAGER_XSERVER_TCP_PORT_6000_OPEN="yes" in /etc/sysconfig/displaymanager
Removed "-nolisten tcp" in file /etc/X11/xdm/Xservers
Add the line "xhost +" to the file /etc/X11/xinit/xinitrc

X works with ssh but not telnet

Thanks

ab
15-Mar-2016, 20:45
If your client machines have X windows (and nothing blocking connections
from the server to those systems using the X protocol) you could
potentially set DISPLAY to the client IP and port, then magically forward
that all directly there (is not really using telnet, but it could be setup
via telnet).

I agree; this (using telnet) is a terrible, horrible, no-good idea. You
may have a lot better luck setting up VNC access to the server, or giving
the end users VMs, or something. Knowing the business case behind this
access/setup may help come up with other ideas.

--
Good luck.

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jmozdzen
16-Mar-2016, 18:47
Hi georgeston,

> X works with ssh but not telnet

it is not clear to me if the clients can reach the server directly, network-wise, and if there are any limits. It might be that using "ssh" creates a tunnel through the ssh connection, allowing to forward the X traffic to the client.

Also, you did not specify on which host you modified the X server configuration - this has to be done on each client's machine.

Please start by trying to connect to port 6000 on an affected client's machine from the server (where the clients try to start the X application), i.e. via "telnet <IP or DNS of client machine> 6000". If telnet establishes a connection, that client's X server is reachable.

Once we know if the networking is right and the user's X server is reachable from your server machine, we can continue to debug why your users cannot connect via their X applications.

Regards,
Jens