Unix and TCP socket specifications may be mixed in any order.
Each element of the list is a list itself, space-separated by default
and changeable in the usual way.
+
+For TCP socket specifications a host name or IP (v4 or v6, but
+subject to list-separator quoting rules) address can be used,
+and the port can be one or a dash-separated pair.
+In the latter case, the range is tried in strict order.
+
Elements after the first for Unix sockets, or second for TCP socket,
are options.
The supported option are: