Test _without_ proper X11 authentication, i.e. DISPLAY and xauth:
> xclock No protocol specified No protocol specified Error: Can't open display: :0.0
T2.1 OK> java plop No protocol specified No protocol specified Exception in thread "main" java.lang.InternalError: Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable. (Stack trace from: GLProfile.initProfilesForDefaultDevices(..) -> NativeWindowFactory.initSingleton(..) -> JAWTUtil.<clinit>-> sun.awt.X11.XToolkit.<clinit> -> sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
T2.2 OK> java -Djava.awt.headless=true plop No protocol specified No protocol specified ... jogamp.opengl.x11.glx.X11GLXDrawableFactory@394a8cd1