enable XDMCP in Fedora Core 2

a.accept 177/udp in firewall
b./etc/rc.d/init.d/xfs：
daemon xfs -droppriv -daemon -port 7100
c./etc/X11/fs/config：
#no-listen = tcp # comment
d./etc/X11/xdm/xdm-config：
! DisplayManager.requestPort: 0 # comment
e./etc/X11/xdm/Xaccess：
* # any host can get a login window (uncomment)
f./etc/X11/gdm/gdm.conf：
RemoteGreeter=/usr/bin/gdmgreeter
Enable=true