Re-enable X11 on Max OS X

Every now and then Apple disables the TCP ports of the X server. I don't know why, but at least two updates from Apple disabled this now.

You know TCP is disabled if you do


netstat -na|grep 6000


and you see nothing. If X11 would be listening you should see something like:


tcp4 0 0 *.6000 *.* LISTEN
tcp6 0 0 *.6000 *.* LISTEN


Also when you try to start an X11 app (like xcalc) from the terminal and you have set the DISPLAY variable to localhost:0, then you will see this if the X server is not listening on TCP (after a few seconds):


Error: Can't open display: localhost:0


To enable TCP on the Xserver type this into a terminal:


defaults write org.x.X11 nolisten_tcp 0


and then restart you X server. Now xcalc should start immediately.