code: function _writeBufferToPort(buffer, transactionId) {
      var transaction = this._transactions[transactionId];
  
      this._port.write(buffer);
      if (transaction) {
          transaction._timeoutFired = false;
          transaction._timeoutHandle = _startTimeout(this._timeout, transaction);
      }
  }
docs: Wrapper method for writing to a port with timeout. <code><b>[this]</b></code> has the context of ModbusRTU
  @param {Buffer} buffer The data to send
  @private