#Can't connect to X11 using ':99'

#Expected Behavior

Application starts normally.

#Actual Behavior

When trying to launch session, session is automatically getting terminated.

#Exception

2019-03-13 03:17:55,383 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257] Exception in thread "main" java.awt.AWTError: Can't connect to X11 window server using ':99' as the value of the DISPLAY variable.
2019-03-13 03:17:55,383 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
2019-03-13 03:17:55,383 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.awt.X11GraphicsEnvironment.access$200(X11GraphicsEnvironment.java:65)
2019-03-13 03:17:55,383 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:115)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at java.security.AccessController.doPrivileged(Native Method)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.awt.X11GraphicsEnvironment.<clinit>(X11GraphicsEnvironment.java:74)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
2019-03-13 03:17:55,384 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at java.lang.reflect.Method.invoke(Method.java:498)
2019-03-13 03:17:55,385 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at org.webswing.toolkit.WebToolkit.init(WebToolkit.java:131)
2019-03-13 03:17:55,385 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at main.Main.initializeExtLibServices(Main.java:139)
2019-03-13 03:17:55,385 ERROR [Webswing Process Handler] (SwingProcessImpl.java:281) [demo_anonym_829470cca8e3_1552461474257]         at main.Main.main(Main.java:44)
2019-03-13 03:17:55,385 INFO  [Webswing Process Handler] (SwingProcessImpl.java:123) [demo_anonym_829470cca8e3_1552461474257] app process terminated.

#Steps to Reproduce the Problem

1. Install Webswing on Linux
2. Start Webswing
3. Start any application through browser

#Solution

This means you do not have an Xvfb session running. Swing requires Xvfb on headless linux to start. Please see Starting on Linux.