code: @Override
  	public void receivePong(Tree message) {
  
  		// Verify protocol version
  		if (checkVersion) {
  			String ver = message.get("ver", "unknown");
  			if (!PROTOCOL_VERSION.equals(ver)) {
  				logger.warn("Invalid protocol version (" + ver + ")!");
  				return;
  			}
  		}
  
  		// Get response's unique ID
  		String id = message.get("id", (String) null);
  		if (id == null || id.isEmpty()) {
  			logger.warn("Missing \"id\" property!", message);
  			return;
  		}
  
  		// Get stored promise
  		PendingPromise pending = promises.remove(id);
  		if (pending == null) {
  			logger.warn("Unknown (maybe timeouted) response received!", message);
  			return;
  		}
  
  		// Resolve Promise
  		pending.promise.complete(message);
  	}
docs: --- RECEIVE PING-PONG RESPONSE ---