(Merge 3.4) Issue #22063: Mention in asyncio documentation that socket

operations require the socket to be non-blocking

Doc/library/asyncio-eventloop.rst

@@ -337,6 +337,8 @@ Low-level socket operations
    representing the data received.  The maximum amount of data to be received
    at once is specified by *nbytes*.
 
+   The socket *sock* must be non-blocking.
+
    This method is a :ref:`coroutine <coroutine>`.
 
    .. seealso::
@@ -351,6 +353,8 @@ Low-level socket operations
    an exception is raised, and there is no way to determine how much data, if
    any, was successfully processed by the receiving end of the connection.
 
+   The socket *sock* must be non-blocking.
+
    This method is a :ref:`coroutine <coroutine>`.
 
    .. seealso::
@@ -367,6 +371,8 @@ Low-level socket operations
    :py:data:`~socket.AF_INET` and :py:data:`~socket.AF_INET6` address families.
    Use :meth:`getaddrinfo` to resolve the hostname asynchronously.
 
+   The socket *sock* must be non-blocking.
+
    This method is a :ref:`coroutine <coroutine>`.
 
    .. seealso::
@@ -384,6 +390,8 @@ Low-level socket operations
    and *address* is the address bound to the socket on the other end of the
    connection.
 
+   The socket *sock* must be non-blocking.
+
    This method is a :ref:`coroutine <coroutine>`.
 
    .. seealso::