xrdp + vnc not working

To allow windows user comfortable access to our SLES server we use xrdp.

Installed packeges are
[]xrdp 0.6.1
]xorg-x11-Xvnc 1.4.1

configuration is vanilla.

When I try to connect to via rdp, I get a login screen, where I can provide my credentials and then select sesman-Xvnc as module

A box pops up with the following content (hand copied)

connecting to sesman ip port 3350 sesman connect ok sending ling info to session manager, please wait... xrdp_mm_process_login_response: login successful for displa[text is truncated here] started connecting connecting to 5937 error - problem connecting

/var/log/xrdp-sesman.log looks good (or at least identical to the one on working installation on sles 11sp4)

[20151023-10:17:03] [INFO ] starting Xvnc session...
[20151023-10:17:03] [INFO ] starting xrdp-sessvc - xpid=24396 - wmpid=24395
[20151023-10:17:06] [INFO ] ++ terminated session:  username XXX, display :36.0, session_pid 24392, ip XXX.XXX.XXX.XXX:52282 - socket: 7
[20151023-10:18:55] [INFO ] scp thread on sck 7 started successfully
[20151023-10:18:55] [INFO ] ++ created session (access granted): username XXX, ip XXX.XXX.XXX.XX:52282 - socket: 7
[20151023-10:18:55] [INFO ] starting Xvnc session.

Interestingly this leaves some processes behind (ps --forest)

24556 ?        00:00:00 Xvnc <defunct>
24555 ?        00:00:00 startwm.sh
24584 ?        00:00:00  \\_ gnome-session

Moreover if start a Xvnc session manually with the identical parameters as specified in the sesman.ini only appended by -rfbauth I am able to connect to that session with Xrdp by choosing the vnc-any module.

I am kind of stuck here and I do not really know where to look for clues, so any help is appreciated.

I got it working and it was really non-obvious and simple. Xvnc does not support 8bits color depth and will silently crash. So on the client side you have to specify a different depth.

It occurred to me after I installed a more recent version of xrdp from X11:RemoteDesktop, which posts the full Xvnc call to the log file