code: @GET
      @Path("subscribeAndUsingExternalThread")
      @Suspend(resumeOnBroadcast = true, listeners = {EventsLogger.class})
      public String subscribeAndResumeUsingExternalThread(final @PathParam("topic") String topic) {
          Executors.newSingleThreadExecutor().submit(new Runnable() {
              public void run() {
                  try {
                      Thread.sleep(5000);
                  } catch (InterruptedException e) {
                  }
                  broadcaster.getBroadcasterConfig().getAtmosphereConfig().getBroadcasterFactory()
                          .lookup(JerseyBroadcaster.class, topic).broadcast("\nEcho: " + topic);
              }
          });
          return "foo";
      }
docs: Suspend the response, and register a {@link AtmosphereResourceEventListener}
  that get notified when events occurs like client disconnection, broadcast
  or when the response get resumed.
  
  @return A {@link Broadcastable} used to broadcast events.