Mac preferences (initializations) are called plists and are stored
in /Users//Library/Preferences
In this directory, com.apple.x11.plist is the relevant one. To view,
nolisten_tcp was set to "1", I changed it to "No" like this:
via web suggestions:
http://lists.apple.com/archives/x11-users/2005/May/msg00073.html
and http://plone.jcu.edu.au/hpc/user-guides/x-environment-for-osx/
but executed slightly differently.