code: public synchronized Boolean sendRaw(byte... rawBytes) {
          if (!start()) {
              log.error("Firmata library is not connected / started! Cannot send bytes {}",
                      FirmataHelper.bytesToHexString(rawBytes));
              return false;
          }
  
          try {
              serialPort.getOutputStream().write(rawBytes);
              return true;
          } catch (IOException e) {
              log.error("Unable to transmit raw bytes through serial port. Bytes: {}",
                      FirmataHelper.bytesToHexString(rawBytes));
              stop();
          }
  
          return false;
      }
docs: Send a series of raw bytes over the serial port to a Firmata supported device.
  
  @param rawBytes byte array to be sent over the SerialPort OutputStream.
  @return True if the bytes were sent. False if the bytes were not sent.