This is a very basic WebSocket chat application based on Java EE 7.
Build with mvn package
.
Deploy to your compliant application server (tested with WildFly 10.1.0 and 14.0.1) by simply copying the war file.
Then open http://localhost:8080/websocket-chat/.
Does not work as-is with Tomcat 8.5.34 or 9.0.12 due to their Session.getOpenSessions() bug, see https://stackoverflow.com/questions/47612057/tomcats-interpretation-of-javax-websocket-sessiongetopensessions.