Files returns a slice containing a `os.File` object for each file descriptor passed to this process via systemd fd-passing protocol.

Listeners returns a slice containing a net.Listener for each matching socket type passed to this process.

ListenersWithNames maps a listener name to a set of net.Listener instances.

PacketConns returns a slice containing a net.PacketConn for each matching socket type passed to this process.

TLSListeners returns a slice containing a net.listener for each matching TCP socket type passed to this process.

TLSListenersWithNames maps a listener name to a net.Listener with the associated TLS configuration.