Django send events via websocket to all clients

Question

I want to send events (json strings) via websocket to all clients (to all who established connection via websocket). My code:

I think that asgi and routing are ok

asgi.py

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'base_app.settings')
django.setup()
application = ProtocolTypeRouter({
    "http": get_asgi_application(),
    "websocket": AuthMiddlewareStack(
        URLRouter(
            websocket_urlpatterns
        )
    ),
})

routing.py

from api_producer.consumers import EventWebSocket

websocket_urlpatterns = [
    url('ws/start/', EventWebSocket.as_asgi()),
]

The problematic point: Some function generates events and I want to send these events to the clients

from api_producer.consumers import EventWebSocket

def event_producer():
    my_socket = EventWebSocket()
    my_socket.receive("Some_text")

consumers.py

from channels.generic.websocket import WebsocketConsumer
from asgiref.sync import async_to_sync


class EventWebSocket(WebsocketConsumer):
    def connect(self):
        self.channel_name = "CHANNEL_1"
        print("CALL_ACCEPT")
        async_to_sync(self.channel_layer.group_add)("global", self.channel_name)
        self.accept()

    def disconnect(self, close_code):
        async_to_sync(self.channel_layer.group_discard)("global", self.channel_name)

    def receive(self, text_data):
        print("RRR_ receive ", text_data)
        async_to_sync(self.channel_layer.group_send)(
            "global",
            {
                "type": "global.message",
                "text": text_data,
            },
        )

    def chat_message(self, event):
        print("CHAT_MESSAGE")
        self.send(text_data=event["text"])
    
    def global_event(self, event):
        print("GLOB_MESSAGE")
        self.send(text_data=event["text"])

My actions: 1 Go to websocketKing and send request ws://127.0.0.1:8000/ws/start/. Log output:

WebSocket HANDSHAKING /ws/start/ [127.0.0.1:37194]
WebSocket HANDSHAKING /ws/start/ [127.0.0.1:37194]
CALL_ACCEPT
HTTP POST /api/start_detection/ 200 [0.57, 127.0.0.1:37238] (trigger event_producer)

What is the proper way to send events?

You need to call self.accept() in the connect method of your consumer to complete the handshake and complete the connection — Iain Shelvington
– Iain Shelvington, Commented Nov 29, 2021 at 18:53
Thank you, added. But I have error: ``` 'EventWebSocket' object has no attribute 'channel_layer``` (in def receive()) — Alex
– Alex, Commented Nov 29, 2021 at 18:57
You shouldn't be initialising an EventWebSocket object and calling receive on it like you are in event_producer. You need to get a channel layer and send a message to a group/channel that all your consumers are members of — Iain Shelvington
– Iain Shelvington, Commented Nov 29, 2021 at 19:07
@IainShelvington could you please elaborate? How to get a channel layer? — Alex
– Alex, Commented Nov 29, 2021 at 19:11

Iain Shelvington · Accepted Answer · 2021-11-29 19:17:17Z

1

You should send the events via a channel layer, you can use channel layers outside of consumers like this

from channels.layers import get_channel_layer
channel_layer = get_channel_layer()

def event_producer():
    async_to_sync(channel_layer. group_send)("global", {
        "type": "global.event",
        "text": "foo"
    })

And in your consumer join the global channel that the event producer sends the events on and add a method that can be triggered by the event producer. You could reuse the "chat" channel...

class EventWebSocket(WebsocketConsumer):
    def connect(self):
        ...
        async_to_sync(self.channel_layer.group_add)("global", self.channel_name)
        self.accept()

    ...

    def global_event(self, event):
        self.send(text_data=event["text"])

answered Nov 29, 2021 at 19:17

Iain Shelvington

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1 Comment

Alex Over a year ago

Updated my code according to your post. But I don't receive any events (no GLOB_MESSAGE and CHAT_MESSAGE output in logs)

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