code: public void addMessageListener(Integer channel, MessageListener<? extends Message> messageListener) {
          addListener(channel, messageListener.getMessageType(), messageListener);
      }
docs: Add a messageListener to the Firmta object which will fire whenever a matching message is received
  over the SerialPort that corresponds to the given channel.
  
  @param channel Integer indicating the specific channel or pin to listen on
  @param messageListener MessageListener object to handle a received Message event over the SerialPort.