Xterm xt error can t open display

This is likely due to either a misconfiguration issue or you have multiple displays. As can be seen in the xterm manpage (man xterm) you can set the display using the -display flag:

   -display display
           This option specifies the X server to contact; see X(7).

If you then look in X(7) where it specifies to look (man X) you will see what you need to put after the flag:

DISPLAY NAMES
       From  the  user's perspective, every X server has a display name of the
       form:

              hostname:displaynumber.screennumber

       This information is used by the application to determine how it  should
       connect  to  the  server  and which screen it should use by default (on
       displays with multiple monitors):

       hostname
               The hostname specifies the name of the  machine  to  which  the
               display is physically connected.  If the hostname is not given,
               the most efficient way of communicating to a server on the same
               machine will be used.

       displaynumber
               The  phrase  "display" is usually used to refer to a collection
               of monitors that share a common set of input devices (keyboard,
               mouse,  tablet, etc.).  Most workstations tend to only have one
               display.  Larger, multi-user systems, however, frequently  have
               several  displays  so  that  more  than one person can be doing
               graphics work at once.  To avoid confusion, each display  on  a
               machine  is assigned a display number (beginning at 0) when the
               X server for that display is started.  The display number  must
               always be given in a display name.

       screennumber
               Some displays share their input devices among two or more moni‐
               tors.  These may be configured  as  a  single  logical  screen,
               which  allows  windows to move across screens, or as individual
               screens, each with their own set  of  windows.   If  configured
               such  that each monitor has its own set of windows, each screen
               is assigned a screen number (beginning at 0) when the X  server
               for  that  display  is  started.   If  the screen number is not
               given, screen 0 will be used.

       On POSIX systems, the default display name is stored  in  your  DISPLAY
       environment  variable.  This variable is set automatically by the xterm
       terminal emulator.  However, when you log into  another  machine  on  a
       network,  you may need to set DISPLAY by hand to point to your display.
       For example,

           % setenv DISPLAY myws:0
           $ DISPLAY=myws:0; export DISPLAY

       The ssh program can be used to start an X program on a remote  machine;
       it automatically sets the DISPLAY variable correctly.

       Finally,  most X programs accept a command line option of -display dis‐
       playname to temporarily override the contents of DISPLAY.  This is most
       commonly used to pop windows on another person's screen or as part of a
       "remote shell" command to start an xterm pointing back to your display.
       For example,

           % xeyes -display joesws:0 -geometry 1000x1000+0+0
           % rsh big xterm -display myws:0 -ls </dev/null &

       X  servers  listen for connections on a variety of different communica‐
       tions channels (network byte  streams,  shared  memory,  etc.).   Since
       there  can be more than one way of contacting a given server, The host‐
       name part of the display name is used to determine the type of  channel
       (also  called  a transport layer) to be used.  X servers generally sup‐
       port the following types of connections:

       local
               The hostname part of the  display  name  should  be  the  empty
               string.   For  example:   :0, :1, and :0.1.  The most efficient
               local transport will be chosen.

       TCPIP
               The hostname part of the display  name  should  be  the  server
               machine's  hostname or IP address.  Full Internet names, abbre‐
               viated names,  IPv4  addresses,  and  IPv6  addresses  are  all
               allowed.     For    example:    x.org:0,    expo:0,    [::1]:0,
               198.112.45.11:0, bigmachine:1, and hydra:0.1.

To get the value of your display you should just be able to run:

echo $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?

In the attached picture is a cygwin terminal window. This is kind of similar to Windows Command Prompt: it cannot display any graphics. To use xterms, you must run the X11 server component of Cygwin, also known as Cygwin-X.

Apparently you’re using the traditional X11 connection procedure, which results in an unencrypted X11 connection: anyone on the same network can spy on your keyboard and mouse actions. But if you need to use it anyway, here’s some diagnostics.

When you start Cygwin-X on Vista for the first time, it is likely that the Windows Firewall or the firewall component of your Windows security solution reports that Cygwin-X is trying to act as a network server on TCP port 6000. To make unencrypted X11 connections work, you must allow this.

When your Cygwin-X (or other X server) is running on your PC, you should be able to reach it from the HP-UX box using telnet to port <DISPLAY number + 6000>. For example:

telnet 192.165.15.3 6000

 This connection will not produce any meaningful command prompt; but if the telnet command says «Connection established» (or the equivalent text for your locale/language), then the unencrypted X11 connection is possible.

However, instead of Cygwin-X I would suggest Xming, for it’s easier to start up and works well with PuTTY’s X11 forwarding function (assuming you use the SSH connection method, not telnet or rlogin).

You can find the latest free Xming and Xming-fonts packages from Sourceforge:

http://sourceforge.net/projects/xming/files/

They are normal Windows self-extracting install packages; just install them using the default values. First Xming, then Xming-fonts.

Then start Xming; it will add its icon in the notification area in the bottom right corner of your screen. You won’t have to do anything else with it.

Then start PuTTY. If you have a pre-configured session, select it and click Load. If you don’t have one, just type the hostname or IP of the HP-UX box to the destination field in the PuTTY configuration dialog. But don’t press Enter or click Login/Open just yet!

Before logging in, go to Connection -> SSH -> X11 in the PuTTY configuration dialog and check the checkbox «Enable X11 forwarding». You can leave the «X display location» field empty. (If you want, you can save the connection settings at this time, with a descriptive name, like «<your HP-UX> with X11») Then start the connection.

When you login with X11 forwarding for the first time, you may see a message telling that sshd has created the $HOME/.Xauthority file on the HP-UX box. If the file already exists, you won’t see this message (and it’s information only anyway).

If the sshd daemon on HP-UX was configured to allow X11 forwarding, your DISPLAY should already be set to a strange-looking value, for example something like 127.0.0.1:10.0. Don’t change it: the value is set automatically by sshd and is required for the SSH X11 forwarding to work. Because sshd also has created the X authority keys for you, you don’t need any «xhost +» commands either.

Now, if you run something like «xterm &» on your PuTTY window, you should get a xterm window on your Windows display. You can run any X11 applications in the same way. If you log out in the PuTTY window, PuTTY is smart enough to wait for the X11 applications to stop before actually closing the connection; but if you force-close PuTTY, all your running remote X11 application windows will be forced to close too.

If you saved the PuTTY connection settings, connecting again will be very simple:

1. make sure Xming is running
2. start PuTTY
3. select the connection settings you saved and click Login (or Open, in some versions of PuTTY)

MK

echo "Test Script"
xterm -e "airodump-ng wlan0mon" & sleep 5
pkill airodump-ng

16 * * * * DISPLAY=:0 xterm -e sudo /home/pi/Desktop/Active/test.sh

#!/bin/bash
echo "Test Script"
xterm -e "airodump-ng wlan0mon" & sleep 4
pkill airodump-ng

sudo bash /home/pi/Desktop/Active/a.sh

12 * * * * sudo bash /home/pi/Desktop/Active/a.sh

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