code: public void connect() throws Exception {
          if (connection != null && !connection.isOpen()) {
              connection.open();
              transaction = connection.getModbusTransport().createTransaction();
              ((ModbusSerialTransaction) transaction).setTransDelayMS(transDelay);
              setTransaction(transaction);
          }
      }
docs: Connects this <tt>ModbusSerialMaster</tt> with the slave.
  
  @throws Exception if the connection cannot be established.