wahello / mergedchat

MultiChat

Basic example of a multi-room chatroom, with messages from all rooms a user is in multiplexed over a single WebSocket connection.

There is no chat persistence; you only see messages sent to a room while you are in that room.

Uses the Django auth system to provide user accounts; users are only able to use the chat once logged in, and this provides their username details for the chatroom.

Some channels can be limited to only "staff" users; the example includes code that checks user credentials on incoming WebSockets to allow or deny them access to chatroom streams based on their staff status.

Installation

Manual installation

Make a new virtualenv for the project, and run:

pip install -r requirements.txt

Then, you'll need Redis running locally; the settings are configured to point to localhost, port 6379, but you can change this in the CHANNEL_LAYERS setting in settings.py.

Finally, run:

python manage.py migrate
python manage.py runserver

Docker installation

Run the app:

docker-compose up -d

The app will now be running on: {your-docker-ip}:8000

Note: You will need to prefix any python manage.py commands with: docker-compose run --rm web. e.g.: docker-compose run --rm web python manage.py createsuperuser

Finally, run:

docker-compose run --rm web python manage.py migrate

Usage

Make yourself a superuser account:

python manage.py createsuperuser

Then, log into http://localhost:8000/admin/ and make a couple of Room objects. Be sure to make one that is set to "staff-only",

Finally, make a second user account in the admin that doesn't have staff privileges. You'll use this to log into the chat in a second window, and to test the authentication on that staff-only room.

Now, open a second window in another browser or in "incognito" mode - you'll be logging in to the same site with two user accounts. Navigate to http://localhost:8000 in both browsers and open the same chatroom.

Now, you can type messages and see them appear on both screens at once. You can join other rooms and try there, and see how you receive messages from all rooms you've currently joined.

If you try and make the non-staff user join your staff-only chatroom, you should see an error as the server-side authentication code kicks in.

How It Works

There's a normal Django view that just serves a HTML page behind the normal @login_required decorator, and that is basically a single-page app with all the JS loaded into the index.html file (as this is an example).

There's a single consumer, which you can see routed to in multichat/routing.py, which is wrapped in the Channels authentication ASGI middleware so it can check that your user is logged in and retrieve it to check access as you ask to join rooms.

Which rooms you are in is kept track of in self.rooms on the consumer so they can be left cleanly if you disconnect.

Whenever the client asks to join a room, leave a room, or send a message, it sends a WebSocket text frame with a JSON encoded command. We use a generic consumer to handle decoding that JSON for us, and then dispatch to one of three handler functions based on what the command is.

All rooms have an associated group, and for joins, leaves and messages, an event is sent over the channel layer to that group. The consumers who are in the group will receive those messages, and the consumer also has handler functions for those (e.g. chat_join), which it uses to encode the events down into the WebSocket wire format before sending them to the client.

Suggested Exercises

If you want to try out making some changes and getting a feel for Channels, here's some ideas and hints on how to do them:

• Make messages from yourself have a different message type. You'll need to edit the chat_message function to send a different packet down to the client based on if the chat.message event it gets is from you or not.
• Add message persistence. There's already a message sent to make a user join a room, so you can use that to send some previous messages; you'll need to make a model to save messages in, though.
• Make the Room list dynamically change as rooms are added and removed. You could add a common group that every socket joins and send events to it as rooms are created/deleted.
• Add message editing and deletion. You'll need to have made them persistent first; make sure you send message IDs down with every message so the client can keep track of them. Then, write some code to handle editing and trigger sending new messages down when this happens with the message ID it's happening to.

Further Reading

You can find the Channels documentation at http://channels.readthedocs.org