WebSockets

As mentioned in Chapter 1, What's in Java EE 8?, while SSE is an HTTP-based standard for one-sided communication, WebSockets is a standard allowing for bidirectional communication between both client and server. WebSockets can be used in scenarios which require two-way communication, such as chat-based applications. WebSockets are published as endpoints using either a programmatic approach or an annotated one.

An endpoint would either extend the javax.websocket.Endpoint class for programmatic style or use the easier approach of using @ServerEndpoint annotation. An endpoint instance is created per connection:

@ServerEndpoint("/chat")
public class ChatEndpoint {
   @OnMessage
   public void onMessage(final Session session, String msg) {
      try {
         session.getBasicRemote().sendText(msg);
      } catch (IOException e) { ... }
   }
}

While this is a simple way to send messages to one connected peer, there's also the possibility of sending a message to all connected peers. This...