XDMCP connection fails for Linux. How do I configure my Linux box?

How to configure Linux XDMCP(KDE/GNOME) settings for Xmanager:

Affected Files

Step 1. Change runlevel to enable gdm or kdm.

1. Open /etc/inittab file.
2. Change the runlevel to 5 as following:

   id:5:initdefault:

Step 2. GDM configuration (When the Linux is using gdm)

1. Open /etc/X11/gdm/gdm.conf file. (/etc/gdm/custom.conf for Fedora Core 5)
2. Go to the [xdmcp] section.
3. Set the value of Enable option to true or 1.

Step 3. KDM configuration (When the Linux is using kdm)

1. Open /etc/X11/xdm/xdm-config file.

2. Comment out "requestPort" option as following:

   DisplayManager.requestPort: 0 
   ==> 
   !DisplayManager.requestPort: 0

3. Open /etc/X11/xdm/Xaccess file.
4. Remove the initial "#" character for the following line:

   #* #any host can get a login window
   ==>
   * #any host can get a login window

5. Open /etc/X11/xdm/kdmrc,
   /usr/share/config/kdm/kdmrc or
   /etc/opt/kde2/share/config/kdm/kdmrc file.
6. Change the value of "Enable" option to "true".

Step 4. Firewall configuration (If the firewall has been configured)

1. Open /etc/sysconfig/ipchains file.
2. Add the following lines at the top of the file:

   -A input -p udp -s 0/0 -d 0/0 177 -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 telnet -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 ssh -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 login -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 exec -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 shell -j ACCEPT
   -A input -p tcp -s 0/0 -d 0/0 7100 -j ACCEPT

Step 5. Restart your Linux to activate the changes.