code: @OnOpen
      public void onOpen(Session session, EndpointConfig config) throws IOException {
          this.session = session;
          session.getBasicRemote().sendText("websocket client ready");
      }
docs: On handshake completed, get the WebSocket Session and send
  a message to ServerEndpoint that WebSocket is ready.
  http://docs.saltstack.com/en/latest/ref/netapi/all/salt.netapi.rest_cherrypy.html#ws
  
  @param session The just started WebSocket {@link Session}.
  @param config The {@link EndpointConfig} containing the handshake informations.
  @throws IOException if something goes wrong sending message to the remote peer