asyncio/Windows: Unix datagram sockets not supported

[basak]

BPO	25230
Nosy	@gvanrossum, @vstinner, @basak, @asvetlov, @1st1

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-03-12.17:03:15.946>
created_at = <Date 2015-09-24.22:14:21.840>
labels = ['type-feature', 'expert-asyncio']
title = 'asyncio/Windows: Unix datagram sockets not supported'
updated_at = <Date 2022-03-12.17:03:15.945>
user = 'https://github.com/basak'

bugs.python.org fields:

activity = <Date 2022-03-12.17:03:15.945>
actor = 'asvetlov'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-12.17:03:15.946>
closer = 'asvetlov'
components = ['asyncio']
creation = <Date 2015-09-24.22:14:21.840>
creator = 'rb'
dependencies = []
files = []
hgrepos = []
issue_num = 25230
keywords = []
message_count = 4.0
messages = ['251549', '251551', '251589', '415001']
nosy_count = 5.0
nosy_names = ['gvanrossum', 'vstinner', 'rb', 'asvetlov', 'yselivanov']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue25230'
versions = ['Python 3.4']

[basak]

AF_UNIX, SOCK_DGRAM sockets are valid, but asyncio doesn't appear to support them.

I've tried combinations of create_connection, create_datagram_endpoint and create_unix_connection, creating a socket myself and passing in sock, and equivalent methods at the server end. There seem to be implicit assumptions about addresses being 2-tuples (instead of strings) and transports being hardcoded to be constructed as either stream or datagram transports. create_unix_connection makes the assumption that it will be a stream, and create_datagram_endpoint that it will be AF_INET or AF_INET6 with (host, port) addressing.

I used 3.4.3, but looking at the docs it doesn't look like this was addressed in 3.5 either.

I'd like this because message boundaries are preserved (unlike in SOCK_STREAM), which if it Just Worked would make local system IPC (eg. with JSON-RPC) extremely trivial to implement in asyncio.

[gvanrossum]

The simplest fix for this IMO is to add a sock parameter to create_datagram_endpoint(). I've filed an issue for this in the upstream asyncio project: python/asyncio#266

[gvanrossum]

See python/asyncio#267. Can you patch that in and see if you can make it work?

[asvetlov]

Implemented a long time ago, closing