Xt error: Can't open display, if using default DISPLAY
Overview
I'm attempting to get XQuartz to work on OSX so I can do X11 forwarding via Docker. I'm following the instructions here. I believe my question may be answered by just the first part, but just in case (to avoid the XY problem), I've provided the second part as well.
Installation
I've installed it via homebrew, via brew cask install xquartz. Then I open -a XQuartz to start it.
Local xterms
Testing it out, if I try to open an xterm, it does not work:
MacBook-Pro:opencv-gui csaftoiu$ xterm
xterm: Xt error: Can't open display: /private/tmp/com.apple.launchd.3wncZULdXC/org.macosforge.xquartz:0
The pseudo-file exists, though:
MacBook-Pro:opencv-gui csaftoiu$ echo $DISPLAY
/private/tmp/com.apple.launchd.3wncZULdXC/org.macosforge.xquartz:0
MacBook-Pro:opencv-gui csaftoiu$ ls -alh $DISPLAY
srw-rw-rw- 1 csaftoiu wheel 0B May 6 21:12 /private/tmp/com.apple.launchd.3wncZULdXC/org.macosforge.xquartz:0
I can open an xterm via XQuartz. Then:
bash-3.2$ echo $DISPLAY
:0
This value works from a regular OSX too:
$ DISPLAY=:0 xterm
# opens xterm, waits for it to finish
$
The following do not work though, not sure why based on the answer here:
xterm: Xt error: Can't open display: localhost:0
MacBook-Pro:opencv-gui csaftoiu$ DISPLAY=127.0.0.1:0 xterm
xterm: Xt error: Can't open display: 127.0.0.1:0
MacBook-Pro:opencv-gui csaftoiu$ DISPLAY=`ipconfig getifaddr en0`:0 xterm
xterm: Xt error: Can't open display: 192.168.1.15:0
Note that xinit does work for some reason:
$ xinit
xinit: XFree86_VT property unexpectedly has 0 items instead of 1
# opens xterm, waits for it to finish
xinit: connection to X server lost
waiting for X server to shut down
Question 1: What is XQuartz actually listening on?
Docker Forwarding with socat
In any case, moving on, this socat command does not work:
MacBook-Pro:opencv-gui csaftoiu$ socat TCP-LISTEN:6000,reuseaddr,fork UNIX-CLIENT:\"$DISPLAY\"
Running that, from another window I do:
MacBook-Pro:opencv-gui csaftoiu$ docker run --rm -it -e DISPLAY=`ipconfig getifaddr en0`:0 ubuntu:14.04 bash
root@912eec31b8cb:/# apt-get update && apt-get install xterm
... such install, wow ...
root@912eec31b8cb:/# xterm
Warning: This program is an suid-root program or is being run by the root user.
The full text of the error or warning message cannot be safely formatted
in this environment. You may get a more descriptive message by running the
program as a non-root user or by removing the suid bit on the executable.
xterm: Xt error: Can't open display: %s
root@912eec31b8cb:/# echo $DISPLAY
192.168.1.15:0
From the socat window I get:
2016/06/14 21:08:15 socat[24289] E connect(5, LEN=68 AF=1 "/private/tmp/com.apple.launchd.3wncZULdXC/org.macosforge.xquartz:0", 68): Connection refused
I can't use the DISPLAY variable that works, either:
MacBook-Pro:opencv-gui csaftoiu$ socat TCP-LISTEN:6000,reuseaddr,fork UNIX-CLIENT:\":0\"
2016/06/14 21:09:43 socat[24309] E connect(5, LEN=4 AF=1 ":0", 4): No such file or directory
Now, this is not a UNIX-CLIENT IP. But, I don't know what DISPLAY=:0 is connecting to. It's certainly not port 6000 since that's the port it used to be listening on. If I change it to 6005, to forward to 6000, and make the Docker container DISPLAY be $(ipconfig getifaddr en0):5 instead, then the connection is of course refused:
$ socat TCP-LISTEN:6005,reuseaddr,fork TCP:localhost:6000
2016/06/14 21:20:32 socat[25379] E connect(8, LEN=16 AF=2 127.0.0.1:6000, 16): Connection refused
Question 2: How to proceed from here?
Answer
I hadn't restarted after re-installing XQuartz. I restarted, and now it works. :).