remote X server display not working

Question

I have a local machine A, and a server B.

from A, I got:

#ps -ef
root      3161  3160  0 09:07 tty1     00:03:04 /usr/bin/Xorg :0 -nr -verbose -auth /var/run/gdm/auth-for-gdm-dJExDH/database vt1

#netstat -nltu
tcp        0      0 0.0.0.0:6000                0.0.0.0:*                   LISTEN      - 

#xhost +
access control disabled, clients can connect from any host

A's ip address is 10.99.54.148

From B, I trid:

#export DISPLAY=10.99.54.148:0.0
#xclock
Xlib: connection to "10.99.54.148:0.0" refused by server
Xlib: No protocol specified

Error: Can't open display: 10.99.54.148:0

I have another desktop C, if I change the DISPLAY to C's IP address, xclock will work. Any suggestion on what to check in A?

Answer 1

Looks as if xclock tries to connect to the x-server using a tcp connection while the x server is not listening to tcp.

In ubuntu that can be changed by:

sudo gedit /etc/gdm/gdm.schemas

find:

<schema>
<key>security/DisallowTCP</key>
<signature>b</signature>
<default>true</default>
</schema>

change from true to false:

<schema>
<key>security/DisallowTCP</key>
<signature>b</signature>
<default>false</default>
</schema>

and then restart gdm.