"Cannot connect to X server" whilest telnetting to another UNIX system
 

From a Fedora Core 1 system terminal window on my gnome desktop, I'm trying to telnet to a Sun UNIX system and run emacs (or any other X-based program). On the Sun, I get "emacs: Cannot connect to X server 10.3.1.40:0.0", but no emacs. The IP address of my Linux system on our local network is 10.3.1.40, so I know DISPLAY is set properly on the Sun, and I've run "xhost +" on the Linux system before telnetting to the Sun, so that's not the problem either.

I'm on a local network in a hospital, and God only knows what the gateway I'm connected to is doing. I have no access to the gateway, and no knowledge other than "it's there and it's probably set to 'Paranoid' mode since we've had so many hacker problems in the past". To confuse things even more (in my mind), I can telnet from one Sun to another and run emacs just fine, it's just the Linux box that's not behaving. So, my question is, what exactly can I ping, probe, stat, cat, or check so I can fix this, or even determine whether it's my problem or a gateway configuration problem? I'm an old, grizzled programmer, but new to this depth of network system administration, so be gentle with me.

Thanks in advance,
Steve

Hmmm, It is late and I am no longer thinking as clearly as I should be, but at the moment the easiest apporach to this problem that I can think of is simply to see if we can go around it. When you get a chance you should try to ssh to the box vice telnet. If the remote box will allow you to make a successful ssh session, then you can try using the -X option on ssh, which handles all of the fun off setting X forwarding for you. The command should look like....

ssh -X user@remote_server

Once you log in, try running 'xeyes' or some other X application to ensure that it worked.

Good luck.

Hi,
Make sure to check the "firewall" setup. The X port (I think it is 6000) may be
blocked. Use "iptables -L -nv" to check the firewall setup (and "man iptables").

Regards,
L Ekman

Nope, and nope. :-(

SSH won't let me get there, and being a brute-force kinda guy, I disabled iptables (using "chkconfig --level 2345 iptables off"), turned off the firewall using redhat-config-securitylevel, and then rebooted the system to make sure that everything was (hopefully) set properly. Still no X-connection was allowed. SHOULD what I did have turned off all protection on the linux side, or is there something else I can try to turn off?

Steve