New install of Fedora Core 5 here...

With Administration -> Security Level And Firewall, I've disabled the firewall and the SELinux stuff.

Step 1) open xterm and enter "xhost +"

Step 2) login to some other machine on my network and enter "export DISPLAY=<my_node>:0". Confirmed display with "echo $DISPLAY"

Setp 3) run something graphical and I get an error saying it can't open the display

I know the issue is with my new Fedora Core 5 machine because it works with other machine. But what's the problem?

How do you login on the other machine, when you use ssh, you can login with the command ssh -X <iporhostname>, then you the client sets the environment up for you.

I was just telneting. It may not be the shortest way, but I'm 110% sure the export display command is right because I do this frequently (on machines other than the one with this new FC5 install).

I think the problem may be this from my ps list:
I tried editing /etc/X11/xdm/kdmrc to remove the nolisten option. But that made no difference. I still get the nolisten option showing up in my process list.

I've also tried a recursive grep from /etc to look for "nolisten" and nothing else that isn't alrady commented out shows up. How can I turn off the Xserver's "nolisten tcp"?

In FC5 you need to edit /etc/gdm/custom.conf and add the following to the [security] section:

If you prefer the GUI, you can run gdmsetup - there should be something along the lines of "Remote login disabled."

--jeremy

I bumped into exactly the same problem and solved just a moment ago, so i hope this could be a help for you, too.

As you have mentioned,

this -nolisten tcp bit was the problem.
I commented the last line of /etc/X11/fs/config, which was saying
no-listen = tcp
(no wonder why couldn't have been grepped with "nolisten")

then added following lines to /etc/gdm/custom.conf
[security]
AllowRemoteRoot=true
DisallowTCP=false

finally I rebooted the system.

Xorg process now became as follows
typed
# xhost +
on Xserver.

then typed
# export DISPLAY=192.168.0.1:0.0
# yast2
on the other machine(SLES9), where 192.168.0.1 is Xserver, and worked fine.