only one event handler at a time for one connection in socket.io

I am creating a node app which will run child process in background.i want to use socket.io to send output from stdout of childprocess to user. when client presses a button event is fired in node server and it runs python script which takes some time.but if users clicks button twice before previous python process is ended 2 python process run simultaneously and corrupt stdout.I want to make sure unless previous python process is completed second python process is not called.I want to make sure only one event handler runs at a time for one connection.

via Manish Madugula