Discovery doesn't work in an async context

[Untit1ed]

i'm trying to call my existing code in an async method, but the following code returns 0 devices:

async def main():
       chromecasts, browser = pychromecast.get_listed_chromecasts(
            friendly_names=["MyChromecastName"])

       if not chromecasts:
            raise RuntimeError('No Chromecast devices on the network')

asyncio.run(main())

I see the same issues with pychromecast.discover_chromecasts. Is there a workaround I could use?

PyChromecast 13.0.5

[mikewebkist]

Another demonstration of the problem:

import asyncio
import pychromecast

def find_chromecasts():
    chromecasts, browser = pychromecast.get_chromecasts()
    print(chromecasts)

async def async_find_chromecasts():
        find_chromecasts()

asyncio.run(async_find_chromecasts())
find_chromecasts()

Calling the find_chromecasts function in the async loop returns an empty list of devices, while the same function outside of the async loop returns whatever's on your network.

[negmos]

I have the same issue.. have you managed to find a workaround?

I'm using FastAPI with a web page to trigger discovery.. it has exactly the same issue

[take-kun]

I could not find a workaround. This seems to be related to the fact that pychromecast is using synchronous implementation of Zeroconf discovery service. This warning is emitted:

zeroconf: unregister_all_services skipped as it does blocking i/o; use AsyncZeroconf with asyncio

[Lamarqe]

I found a solution to the problem.

There is a magic in zeroconf which automatically discovers if its created in an async loop or in a threaded environment.
When you create the zeroconf instance outside of async and hand it over to pychromecast, the example above succeeds:

zconf = zeroconf.Zeroconf()

async def main():
       chromecasts, browser = pychromecast.get_listed_chromecasts(
            friendly_names=["MyChromecastName"], zeroconf_instance=zconf)

       if not chromecasts:
            raise RuntimeError('No Chromecast devices on the network')

asyncio.run(main())

[Lamarqe]

For the example of @mikewebkist regarding get_chromecasts(), you should useblocking=False:

import asyncio
import pychromecast

async def find_chromecasts():
    done = asyncio.Event()
    loop = asyncio.get_running_loop()
    def callback(chromecast):
        loop.call_soon_threadsafe(done.set)
        loop.call_soon_threadsafe(done.clear)
    browser = pychromecast.get_chromecasts(blocking=False, callback=callback)
    expected_devices = 1
    for _ in range(expected_devices):
        await done.wait()
    print(browser.devices)

asyncio.run(find_chromecasts())