I'm struggling to set up X-forwarding between 2 different machines on my local network and my ubuntu desktop. I'm able to connect using ssh x-forwarding one one machine, but the other machine (a Qnap TS-219P II) seems to have a less functional build of SSH on it, and I'd rather use a simpler approach.

I've set $DISPLAY, and done 'xauth list $DISPLAY' on the desktop, then 'xauth add ' on the remote machine.

From the remote machine, I just get

xterm
xterm Xt error: Can't open display: 192.168.0.4:0.0

Now, oddly, if I connect via ssh -X, there is a different magic cookie for the tunnelled port (but neither seems to work). I'm wondering if there is a port which needs to be enabled to permit X connections from the LAN? If so, how?

The proper solution might be to re-build all the packages which are preventing X-forwarding from working on my QNAP machine, but lets assume for the purposes of this question that I've tried building enough packages on that architecture already and want to run X without the overhead of encryption.