There are a couple more software programs involved: serial port emulators. I use 'com0com' 64 bit on the dependent computers:
and N8VBvCom on the old 32 bit main computer:
The Main Computer's VVP:
and the Main Computer's VVP Settings:
The Dependent Computer's VVP:
and the Dependent Computer's VVP Settings:
In essence it isn't a trivial exercise to get everything set up properly so it works. But it's well worth the effort.
(And as you can see my setup is very much 'over-the-top' with the backup computers and all.)