Tutorial Part 2: Write a chat consumer

Create chat/consumers.py and define a Socket.IO consumer.

# chat/consumers.py
from sio import SocketIOConsumer

class ChatConsumer(SocketIOConsumer):
    namespace = "/chat"

    async def connect(self, socket, auth):
        # Put this client into a logical room.
        await socket.join("lobby")

        # Send an initial message only to this client.
        await socket.emit("system_message", {"text": "Welcome!"})

        # Return True to accept the Socket.IO namespace connection.
        return True

    async def disconnect(self, socket, reason):
        # Optional cleanup can go here.
        pass

    async def event_chat_message(self, socket, payload, ack=None):
        text = payload.get("text", "")

        # Broadcast to everyone in the room.
        await socket.server.emit(
            "chat_message",
            {"text": text},
            room="lobby",
            namespace=socket.namespace,
        )

        # Optional ack back to the caller.
        if ack is not None:
            await ack({"status": "ok"})

What each method does

namespace = "/chat"

Registers this consumer for the Socket.IO namespace named /chat.

connect(self, socket, auth)

Runs when the client connects to the namespace. The auth argument is the authentication payload sent by the Socket.IO client. Return True to accept the connection.

disconnect(self, socket, reason)

Runs when the namespace socket disconnects. Use it for optional cleanup.

event_chat_message(self, socket, payload, ack=None)

Handles the Socket.IO event named chat_message. Any method named event_<name> becomes the handler for the event named <name>.

The socket object

The socket argument represents this connected client in this namespace. In this tutorial you use it to:

• join the lobby room with socket.join("lobby");

• emit to the current client with socket.emit(...);

• broadcast through the server with socket.server.emit(...);

• keep broadcasts scoped to the current namespace with namespace=socket.namespace.

In the next part you mount this consumer in ASGI routing and connect a browser client.