WebSockets come with Java EE 7 and require no additional dependencies or libraries. Particularly in "microservices architectures" websockets are an interesting option for the implementation of WAR to WAR communication.

In this screencast I created two WARs from scratch and let them communicate via WebSockets:

See you at Java EE Microservices. Is Munich's airport too far? Learn from home: javaeemicro.services.