> In writing a simple UDP client using asyncio, I tripped over a call to getsockname() in the _SelectorTransport class in asyncio/selector_events.py. (...)

This bug has been fixed recently by:

commit 63deaa5b70108ef441c57728322da6b4321db4fc
Author: Vincent Michel <vxgmichel@gmail.com>
Date:   Tue May 7 19:18:49 2019 +0200

    bpo-31922: Do not connect UDP sockets when broadcast is allowed (GH-423)


Extract of the change:

diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 93b6889509..29968214f8 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -587,7 +587,10 @@ class _SelectorTransport(transports._FlowControlMixin,
     def __init__(self, loop, sock, protocol, extra=None, server=None):
         super().__init__(extra, loop)
         self._extra['socket'] = sock
-        self._extra['sockname'] = sock.getsockname()
+        try:
+            self._extra['sockname'] = sock.getsockname()
+        except OSError:
+            self._extra['sockname'] = None
         if 'peername' not in self._extra:
             try:
                 self._extra['peername'] = sock.getpeername()


Thanks for your contribution and your proposed patch Paul McGuire! Sorry for the late reply. I mark this change as a duplicate of bpo-31922.