websocket-java
Ref 1: https://github.com/TooTallNate/Java-WebSocket #Project based on Java WebSockets
Ref 2: https://blog.openshift.com/how-to-build-java-websocket-applications-using-the-jsr-356-api/
Ref 3: https://examples.javacodegeeks.com/enterprise-java/jetty/jetty-websocket-example/ . Jetty