I know a very similar question has been asked in the past (Connect two VMs on two different physical machines into their own network) but the reason why this one shouldn't be considered a duplicate is that I'm asking for a bit more, including virtual serial cable. The question Connect two virtualmachines on different host machines is rather different from mine as I'm trying to emulate the physical cable connection rather than join virtual machines to the network in which hosts reside.
To elaborate, I have two virtual PC machines, each running on its own host using VirtualBox. Both hosts are Windows 10. In the future I may want to use more hosts, of which some may be running Linux. There are two things I'd like to achieve:
1 Connect two virtual machines on separate hosts with a virtual serial cable (null modem cable)
2 Connect virtual machines on separate hosts with virtual network cables, so create a virtual isolated LAN, over which I could mess around with different network protocols, like IPX.
Yes, it's for gaming... Also for experiments.
Anyway, I am aware that it's technically possible. It's possible to emulate various PCs and those PCs having various peripherals like serial ports and network adapters. That exists, e.g. VirtualBox. It's possible for two such emulators running on separate computers communicate to each other (via LAN or through the internet) and emulate a cable (through that communication) plugged into both virtual PCs. But does that exist, has it been implemented?
So is what I'm asking possible with existing software, preferably VirtualBox and with not too many plug-ins? Through the internet or just through a LAN?