X11 forwarding not working

I often need to launch X11 applications on aix servers and have their graphical output on my linux workstation.

On the web there are a lot of guides , that indicate many useful checks ...but also applying those workarounds

i couldn't get my environment working.

I encountered a curious problem , here follow some details:

on my wks i type :

user@client:~> ssh -vv -Y server

...
...
user@server's password:

X11 forwarding request failed on channel 0


I tried launching xclock

user@server:/home/user#xclock
Error: Can't open display:


going deeper in analysis , i found :

#tail -40f /var/log/messages

Nov 11 12:41:43 server auth|security:err|error sshd[761876]: error: Failed to allocate internet-domain X11 display socket.
Nov 11 12:45:46 server auth|security:err|error sshd[1171700]: error: Failed to allocate internet-domain X11 display socket.


Seeking this error on the web i found some useful links about ipv6 related problems, so i tried to stop sshd :

root@server:/#stopsrc -s sshd
0513-044 The sshd Subsystem was requested to stop.
root@server:/#/usr/sbin/sshd -4


and retry from the client :

debug2: X11 forwarding request accepted on channel 0
..
..
1356-364 /usr/X11R6/bin/xauth: creating new authority file /home/user/.Xauthority
user@server:/home/user#


now the X11 forwarding request is accepted correctly, also xclock test is successful.

So i can start to fix the problem:

kill the temporary sshd

open /etc/ssh/sshd_config and modify the following block

#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

in

AddressFamily inet
ListenAddress 0.0.0.0

and verify that other X11 directives are ok :

X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost no


and now ...

root@server:/#startsrc -s sshd
0513-059 The sshd Subsystem has been started. Subsystem PID is 655738.

Last try , let's check ... all is ok now.