the usual systemd socket activation protocol) that it shall respond to Varlink queries via a passed in socket fd.
The path may also be prefixed with "ssh-unix:" in which case an SSH connection is made to some remote Varlink service.
New with v257 is that "ssh-exec:" is now also available which also sets up an SSH connection, but invokes a specified binary on the remote side, talking to it via standard input/output.
All four ways to communicate (connect to AF_UNIX socket, execute binary, …