VNC connection on Xen Hypervisor.

Enable VNC in Xen config file:
/etc/xen/xend-config.sxp

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(vnc-listen '0.0.0.0')
(vncpasswd 'secret')

Make sure you restart xend service afterwards:
/etc/init.d/xend restart 

Connect to the VM via VNC
vnc-viewer xxx.xxx.xxx.xxx:0