It can all be scripted, but that "connection" has to be rock solid during the "synch". There are 3rd party solutions available, such as GoZync from SeedCode that do this and they do not use a plug in to do it. 360works also offers a synch tool, but I don't recall if it is only for FM GO or can also be used with FM PRo the way GoZync can or not.
The process can be very complex depending on the structure of your database and whether two different copies of the database might have altered the same record but in different ways since the last synch or not. (even commercial synch solutions might only manage to keep one of the two changes...)
FileMaker Pro databases can be very easily synchronised / syncrhonized as per video FileMaker Pro Database synchronisation / synchronization - Sync Pro - YouTube
ONE (1) click and no touch - fully and totally automatic