All my attempts to access a CentOS 7 machine from Fedora 20 using x2go have failed with these error messages in /var/log/secure:

Nov 17 16:42:08 datium sshd[4175]: Accepted publickey for dad from
127.0.0.1 port 43005 ssh2: RSA
c5:d0:02:e7:90:ce:8b:bb:65:b2:78:66:29:8c:c8:15
Nov 17 16:42:08 datium sshd[4175]: pam_unix(sshd:session): session
opened for user dad by (uid=0)
Nov 17 16:42:08 datium sshd[4185]: subsystem request for sftp by
user dad
Nov 17 16:42:09 datium sshd[4185]: Received disconnect from
127.0.0.1: 11: disconnected by user
Nov 17 16:42:09 datium sshd[4175]: pam_unix(sshd:session): session
closed for user dad

The CentOS 7 machine is virtualized in kvm, running on another F20
machine, but that shouldn’t matter. ssh is configured to allow access via public/private keys and works fine. sshd seems to have a problem with “subsystem request for sftp”, whatever that means, but I have verified that I can run ‘sftp datwizkvm’
and get access to my home directory there.

When x2go has negotiated the public key transaction, an XFCE window pops up for about 1 sec and then vanishes. This leads me to speculate that the problem is more to do with starting X than making the connection.

In the opposite direction, x2goclient on the CentOS 7 machine will happily open and run an XFCE display of the Fedora 20 machine.

Does anyone have insight about why the connection is asymmetric?
Has anyone experienced this kind of failure?
Any hints how to fix it?