Claim a slot: the first call allocates the listen port and returns the 'listen' role; every later call returns 'connect' towards that port.
127.0.0.1:<listenPort> — the address subsequent VMs connect to.
Host port the first-attached VM listens on. 0 until the first attach().
Shared VM-to-VM network over QEMU socket netdevs. Pass one instance as
networkto every VirtualMachine that should share a segment: the first to attach listens on an allocated host port (default range 5555–5599), the rest connect to it.