xdm xdmcp support broken after recent update

[tonyw]

The venerable xdm provides support for xdmcp as needed for remote logins and Xvnc. It had been working fine until recently when an update seemed to have broken xdm support for xdmcp. Note that xdm itself does not appear to have been updated in years. xdm is especially needed when the preferred display manager for local logins does not support xdmcp.

The problem is clear enough using the output from netstat -tl. Normally, xdm should be listening on the IPv6 port 177/xdmcp. Instead it seems to be listening on a random port which changes each time it is invoked. Telneting to this port with xdm in debug mode confirms that this is the xdmcp port.

[tonyw (tony-whyman)]

Forgot to mention that I am using Ubuntu 14.04