bpo-33921: Clarify how to bind to all interfaces using socket (GH-7877)

Clarify how to bind to all interfaces using socket

Author: johnthagen

Doc/library/socket.rst

@@ -70,6 +70,13 @@ created.  Socket addresses are represented as follows:
   notation like ``'daring.cwi.nl'`` or an IPv4 address like ``'100.50.200.5'``,
   and *port* is an integer.
 
+  - For IPv4 addresses, two special forms are accepted instead of a host
+    address: ``''`` represents :const:`INADDR_ANY`, which is used to bind to all
+    interfaces, and the string ``'<broadcast>'`` represents
+    :const:`INADDR_BROADCAST`.  This behavior is not compatible with IPv6,
+    therefore, you may want to avoid these if you intend to support IPv6 with your
+    Python programs.
+
 - For :const:`AF_INET6` address family, a four-tuple ``(host, port, flowinfo,
   scopeid)`` is used, where *flowinfo* and *scopeid* represent the ``sin6_flowinfo``
   and ``sin6_scope_id`` members in :const:`struct sockaddr_in6` in C.  For
@@ -171,12 +178,6 @@ created.  Socket addresses are represented as follows:
 
   .. XXX document them!
 
-For IPv4 addresses, two special forms are accepted instead of a host address:
-the empty string represents :const:`INADDR_ANY`, and the string
-``'<broadcast>'`` represents :const:`INADDR_BROADCAST`.  This behavior is not
-compatible with IPv6, therefore, you may want to avoid these if you intend
-to support IPv6 with your Python programs.
-
 If you use a hostname in the *host* portion of IPv4/v6 socket address, the
 program may show a nondeterministic behavior, as Python uses the first address
 returned from the DNS resolution.  The socket address will be resolved