I have an Iskara MT-860S energy meter with dual RS-485 port. I am trying to handshake in with Termite but could not receive any response. Rx light on meter blinks when packet is received but no Tx light is lit. I am using " /?!\r\n ", " /?139\r\n " as meter address is 139, COM port parameters 300 7E1 and 9600 8N1 were attempted. Can anyone help me in getting the meter handshake with Termite ?

 

That meter communicates using the IEC 62056-21 protocol.
https://en.wikipedia.org/wiki/IEC_62056#IEC_62056-21

Therefore, I don't think you can use Termite and simply send ASCII commands.

Take a look at these software tools/libraries instead:
https://www.aggsoft.com/serial-data-logger/tutorials/iec62056-power-meter-data-logging.htm
https://wigersma-sikkema.com/en/downloads-2/software/
https://www.openmuc.org/iec-62056-21/