SocketControlMessage] contains a [class@Gio.UnixFDList]. It may be sent using [method@Gio.Socket.send_message] and received using [
method@Gio.Socket.receive_message] over UNIX sockets (ie: sockets in the `G_SOCKET_FAMILY_UNIX` family). The file descriptors are copied
between processes by the kernel.
For an easier way to send and receive file descriptors over stream-oriented UNIX sockets, see [method@Gio.UnixConnection.send_fd] and [
method@Gio.UnixConnection.receive_fd].
Note that `<gio/gunixfdmessage.h>` belongs to the UNIX-specific GIO interfaces, thus you have to use the `gio-unix-2.0.pc`
pkg-config file or the `GioUnix-2.0` GIR namespace when using it.