This is a demo server, use Java websocket library and Tyrus server. With this code that using Tyrus standalone, you can run your server as a pure program without server emvironment such as Apache Tomcat... This code used to interect with PrettyWebsocket Unity plugin, is a part of any game online project using Unity3D engine.
The easiest way to run this code, that's download the Eclipse IDE: https://www.eclipse.org/downloads/eclipse-packages/ Eclipse for Java Developers is enough, no need Java EE. Download this source code and import into Eclipse, run MyApp project.
You can read more information at https://tyrus.java.net/documentation/1.13/user-guide.html