i have setup XDMCP successfully on Fedora without any issues, however i have problem in setting up XDMCP on Redhat Enterprise Linux 5. i have enabled the remote login option using 'gdmsetup' [remote login set to => ['same as local'] . i have also made sure that "/etc/gdm/custom.conf" file has the following code

[xdmcp]
Enable=true.

i have restarted the machine but still i can not see this RHEL machine on X server software. i am trying to remote login from WinXP system to RHEL5 machine using Xserver.

in some of the article it says /etc/X11/gdm/xxxx but i do not see gdm folder under /etc/X11. other article tells me that RHEL5 location is /etc/gdm.

another interesting thing is that i can NOT telnet to this RHEL system from outside that machine. however i can telnet within that system. so i checked the /etc/hosts.allow and made sure that it has '*' to allow all systems. i do not see anything under /etc/hosts.deny!

however i can ping within the system and ALSO from outside this machine.

any idea on how can i fix this?

Try

# service iptables stop

...and try again.

If that solves your problem, you'll need to figure out how to modify the iptables firewall to permit the traffic you want (X, xdmcpd, and apparently telnet).

Thanks Mackdav . That worked for me.

After that I opened up ports for XDMCP using the following:

XDMCP uses TCP, UDP port 177 and TCP port 6000 to 6005

Source: http://www.tldp.org/HOWTO/XDMCP-HOWTO/procedure.html

It worked after a iptables restart, but I went ahead and rebooted the system just to be 100% sure.

I haven't had any issues.