Hi, I was trying this out: Server code: def dataReceived(self, data): if (args["cmd"] == "CHECK_IN"): foo = subprocess.Popen('python master.py',shell = True) *# this ACK notifies the client to close the connection* self.transport.write( self.create_message("CHECK_IN","ACK") ) I use the subprocess call , as I want to avoid threads here, and independently launch my master.py without blocking this code. I dont aim to have any interaction with the master.py once it is launched Now, I see unpredictable behaviour here.. I have been trying many times, but the subprocess call does not happen everytime ! The connection is closed by the client without the master getting launched in some cases. How does the transport.write behave in such cases.. Do you people see a structural problem here.. Or adding some small delay of 2 sec before transport.write might help? Regards Naman