On the Lucid box that is working with XDMCP, I just confirm that port 177 is only opened for IPV6:
$ sudo netstat -atnup | grep 177 udp6 0 0 :::177 :::* 754/gdm-binary $
On the Lucid box that is working with XDMCP, I just confirm that port 177 is only opened for IPV6:
$ sudo netstat -atnup | grep 177
udp6 0 0 :::177 :::* 754/gdm-binary
$