GH-88968: Add notes about socket ownership transfers

Doc/library/asyncio-eventloop.rst

@@ -468,6 +468,12 @@ Opening network connections
      *happy_eyeballs_delay*, *interleave*
      and *local_addr* should be specified.
 
+     .. note::
+
+         The *sock* argument transfers ownership of the socket to the
+         transport created. To close the socket, call the transport's
+         :meth:`~asyncio.BaseTransport.close` method.
+
    * *local_addr*, if given, is a ``(local_host, local_port)`` tuple used
      to bind the socket locally.  The *local_host* and *local_port*
      are looked up using ``getaddrinfo()``, similarly to *host* and *port*.
@@ -577,6 +583,12 @@ Opening network connections
      transport. If specified, *local_addr* and *remote_addr* should be omitted
      (must be :const:`None`).
 
+     .. note::
+
+         The *sock* argument transfers ownership of the socket to the
+         transport created. To close the socket, call the transport's
+         :meth:`~asyncio.BaseTransport.close` method.
+
    See :ref:`UDP echo client protocol <asyncio-udp-echo-client-protocol>` and
    :ref:`UDP echo server protocol <asyncio-udp-echo-server-protocol>` examples.
 
@@ -688,6 +700,12 @@ Creating network servers
    * *sock* can optionally be specified in order to use a preexisting
      socket object. If specified, *host* and *port* must not be specified.
 
+     .. note::
+
+         The *sock* argument transfers ownership of the socket to the
+         server created. To close the socket, call the server's
+         :meth:`~asyncio.Server.close` method.
+
    * *backlog* is the maximum number of queued connections passed to
      :meth:`~socket.socket.listen` (defaults to 100).
 
@@ -789,6 +807,12 @@ Creating network servers
    * *sock* is a preexisting socket object returned from
      :meth:`socket.accept <socket.socket.accept>`.
 
+     .. note::
+
+         The *sock* argument transfers ownership of the socket to the
+         transport created. To close the socket, call the transport's
+         :meth:`~asyncio.BaseTransport.close` method.
+
    * *ssl* can be set to an :class:`~ssl.SSLContext` to enable SSL over
      the accepted connections.