Yes when stop button is pressed, connection to PLC should be closed ? In same time message about connection should be changed from Connect to Disconnect. Right now the way how it working application is started message is Disconnected, user give some parameters select port and press Start button, that check trigger DataRecived event, and if data is received from PLC, message about connection changes to Connect. But when I press stop and when I am not receiving data from plc anymore, message still showing connected, and I would like to change that message to Disconnected ?