This is a demo of using the Python Starlette framework for websockets-based subscription to server events on multiple, dynamically created and deleted channels.

Run with

pipenv --python 3.8
pipenv shell
pipenv install
uvicorn starlette_websocket_demo:app

Protocol

This is meant to be server-sent events, which are implemented via the websockets. However, for convenient usage demonstration, there are some HTTP endpoints for channel management and sending messages

Websocket protocol

Client messages

• subtest123: subscribe me to channel test123
• poptest123: unsubscribe me from channel test123

Server messages

JSON formatted. Message type is stored in field t, channel id is in field id.

• type new: new channel advertisement – means that the given channel was just created and can be subscribed to
• type del: channel deletion notice – the given channel was deleted, and the client automatically unsubscribed
• type msg: incoming message – a message was sent to the given channel, the message data are stored under the field msg (can be structured data)

All channels are automatically unsubscribed upon disconnection (from any side). No messages are preserved on server, they are just sent to all clients subscribed to the given channel at the moment the message was received.

HTTP endpoints

• GET /new-channel?id={id} – create a channel with the given ID (will be immediately advertised to clients)
• GET /del-channel?id={id} – delete the channel with the given ID
• POST /push/{id} – send a message to the channel with the given ID, the data is application/json in the request body