code: public void setRequest(ModbusRequest req) {
          request = req;
          if (req != null) {
              request.setTransactionID(getTransactionID());
          }
      }
docs: Sets the <tt>ModbusRequest</tt> for this
  <tt>ModbusTransaction</tt>.<p>
  The related <tt>ModbusResponse</tt> is acquired
  from the passed in <tt>ModbusRequest</tt> instance.<br>
  <p>
  
  @param req a <tt>ModbusRequest</tt>.