[gdm-list] How to enable the gdm listening for XDMCP on port 177 via ipv6 ?

["tiger" <345220094 qq com>]

Hello everyone:

        I'm a user of the gnome desktop.I have been encountered a trouble which my gdm can't listen on port 177 via ipv6 when I enable the XDMCP.

This is my version of gdm. 

[root@localhost ~]# gdm-binary --version
GDM 2.30.4

This is the content of my configuration file --"/etc/gdm/custom.conf"

# GDM configuration storage
[daemon]
[security]
AllowRemoteRoot=true
DisallowTCP=false
[xdmcp]
Enable=true
[greeter]
[chooser]
[debug]

[root@localhost ~]# lsof -i:177
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
gdm-binar 4082 root   11u  IPv4  25778      0t0  UDP *:xdmcp 

Can anyone help me to solve this problem ?

Thank you very much!