I know this has been asked/answered a lot, but I'm pretty sure I'm doing it right, though if I was it would work! This involved 2 linux boxes.

On the system running X, I issue the command "xhost +" and it tells me "access control is disabled, client can connect from any host"

I then log into another host and "export DISPLAY=firsthost:0.0" and run xclock or xterm. In both cases the system thinks for a little while and then tells me "unable to open display"

gotta be something silly but I just don't see what.
I've always done this exporting linux displays to my PC running an X server and it just works. The only thing I'm doing different here is the xhost command, and trying to export onto an X server running on linux.

-mark

Well, it is something simple. Chances are, your Xserver on your local Linux box is running with the "-nolisten" option to X (more secure). You don't say what version/distro of Linux you're using, so it's hard to give you details...Google can probably point you to how to turn off that option, then things should work from there.

Sorry about that... It's RHEL5.2 and yes, I see -nolisten on the command line. what's the best way to remove it?
-mark

I'm not very familiar with doing that under RHEL5, but check the /etc/X11/xinit/xserverrc file. Change the DisallowTCP from "false" to "true", and restart.