But my data in coming in continuously.
It is a scanning process. Come in in every 30-35 secs.

>Sure it will, for a number of events beyond just receiving data:
>

>Constant 	Value 	Description
>
>comEvSend 	1 	There are fewer than Sthreshold number of characters in the transmit buffer.
>comEvReceive 	2 	Received Rthreshold number of characters. This event is generated continuously until you use the Input property to remove the data from the receive buffer.
>comEvCTS 	3 	Change in Clear To Send line.
>comEvDSR 	4 	Change in Data Set Ready line. This event is only fired when DSR changes from 1 to 0.
>comEvCD 	5 	Change in Carrier Detect line.
>comEvRing 	6 	Ring detected. Some UARTs (universal asynchronous receiver-transmitters) may not support this event.
>comEvEOF 	7 	End Of File (ASCII character 26) character received.
>

>

>So with no incoming data, you should be able to sense a state change, indicating the cause.
>
>>But onComm event won't be fired because com port does not send any data to the control.