How to make X.org listen to remote connections

Based on information found in this page about enabling XDCMP and the file /etc/gdm/gdm.schemas, I managed to create a /etc/gdm/custom.conf file:

# /etc/gdm/custom.conf
[xdmcp]

[chooser]

[security]
DisallowTCP=false

[debug]

Take care with letter case: it won't work, if you write "disallowTCP=false"... I also changed the /etc/X11/xinit/xserverrc file to:

exec /usr/bin/X11/X

i.e. I removed the -nolisten tcp options to the X executable. I don't know if I needed to. You might want to try avoiding this edit.

If you only change the xserverrc file, X will nevertheless start with "-nolisten TCP".

After that, all that is needed is a restart of the gdm process:

sudo service gdm restart

You can verify the success as:

tzot@tzot-laptop:/etc/X11
$ netstat -an | grep -F 6000
tcp 0 0 0.0.0.0:6000 0.0.0.0:* LISTEN
tcp6 0 0 :::6000 :::* LISTEN
Synopsis

So, in 10.10 this still works: create /etc/gdm/custom.conf with contents as specified above and restart gdm.