private void cmbCarbinetIndex_SelectedIndexChanged(object sender, EventArgs e)
        {
            this.ClearListenerAndStopRunning();
            this.ClearControls();

            this.current_helper = helperList[this.cmbCarbinetIndex.SelectedIndex];
            this.current_helper.start(this);
        }
        void initialHelperList()
        {
            EpcProductHelper helper1 = new EpcProductHelper(this.listening_port1);

            this.helperList.Add(helper1);
            EpcProductHelper helper2 = new EpcProductHelper(this.listening_port2);

            this.helperList.Add(helper2);
            EpcProductHelper helper3 = new EpcProductHelper(this.listening_port3);

            this.helperList.Add(helper3);
            EpcProductHelper helper4 = new EpcProductHelper(this.listening_port4);

            this.helperList.Add(helper4);
        }