In order to communicate an application from device A to an application on device B, there must be some network or connection that connects both the Internet, Bluetooh, WiFi, cable connections, and so on. But as you said not that you did not want to use Web Service or Server you will need to use one of the Wired, Bluetooh or WiFi functionality. So I recommend that you use a Server for this, since desktops do not have WiFi and the older laptops also do not have this functionality. Already bluetooh I will not mention since there are few laptops that have bluetoothh integrated functionality and those who have let's say so are not conventional for most of the population. Sorry for the response is incomplete or is not as desired, for min your question lacks some specific information