[issue21701] create_datagram_endpoint does not receive when both local_addr and remote_addr provided

[Allen Riddell]

New submission from Allen Riddell:

Creating a UDP connection through ``create_datagram_endpoint`` when specifying both remote_addr and local_addr does not work; messages are not received. If remote_addr is removed, messages are received.

Easy to reproduce:

works: python3 client_good.py & python3 sender.py 127.0.0.1 8888
blocks?: python3 client_bad.py & python3 sender.py 127.0.0.1 8888

>From the PEP I gather this really is a bug, since create_datagram_endpoint is supposed to be bidirectional::

    create_datagram_endpoint(protocol_factory, local_addr=None, remote_addr=None, <options>). Creates an endpoint for sending and receiving datagrams (typically UDP packets). Because of the nature of datagram traffic, there are no separate calls to set up client and server side, since usually a single endpoint acts as both client and server.

----------
components: asyncio
messages: 220134
nosy: ariddell, gvanrossum, haypo, yselivanov
priority: normal
severity: normal
status: open
title: create_datagram_endpoint does not receive when both local_addr and remote_addr provided
type: behavior
versions: Python 3.4, Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21701>
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