code: public synchronized Boolean sendMessage(TransmittableMessage message) {
          if (!start()) {
              log.error("Firmata library is not connected / started! Cannot send message {}",
                      message.getClass().getSimpleName());
              return false;
          }
  
          try {
              log.debug("Transmitting message {}. Bytes: {}", message.getClass().getSimpleName(),
                      FirmataHelper.bytesToHexString(message.toByteArray()));
              serialPort.getOutputStream().write(message.toByteArray());
              return true;
          } catch (IOException e) {
              log.error("Unable to transmit message {} through serial port", message.getClass().getName());
              stop();
          }
  
          return false;
      }
docs: Send a Message over the serial port to a Firmata supported device.
  
  @param message TransmittableMessage object used to translate a series of bytes to the SerialPort.
  @return True if the Message sent. False if the Message was not sent.