How do I have a long-lasting client?

[inklesspen]

I am writing an async app (using Trio). I have an Application class with various async "handle_x_event" methods that get scheduled in the Trio nursery. Some such events need to trigger a gRPC call.

Currently, this only works if I create the channel and stub right when I need to use it:

class Application:
    def __init__(self):
        # various setup omitted

    async def handle_keystrokes(self):
        # handle some keys

    async def handle_document_updates(self):
        # handle document changes

    async def handle_screen_updates(self):
        async for _ in self.screen_update.events():
            logging.debug("sending screen update")
            req = self.make_request()
            logging.debug("sending {!r}".format(req))
            async with purerpc.insecure_channel('127.0.0.1', TABULA_PORT) as rpc_channel:
                stub = imprimare_grpc.TabulaStub(rpc_channel)
                response = await stub.UpdateDisplay(req)
            logging.debug(response)

async def main():
    async with trio.open_nursery() as nursery:
        application = Application()
        nursery.start_soon(application.handle_keystrokes)
        nursery.start_soon(application.handle_document_updates)
        nursery.start_soon(application.handle_screen_updates)

If I try to create the rpc_channel or the stub in my main function and pass it in to the Application class for use, then the await stub.UpdateDisplay(req) call never returns. There's no error message; that task just silently waits forever, and the server does not receive my request.

I want a long-lasting client connection. How can I set one up?