simplest nontrivial example I could come up with of using websockets to push data from server to client

App.js

// *really* simple example of browser client subscribing the reddit comments via websocket
// this is how a server can push state to a web client
// things like push notification etc

// use create-react-app to create a React application
// replace src/App.js with the contents of this file
// then run the app with `npm start` and `ws_server.py` running
// and open a web console. You should see reddit comments printed live in the console

// ripped and modified from here: https://stackoverflow.com/a/60161181

import logo from './logo.svg';
import './App.css';
import React, {useEffect, useRef, useState} from 'react';

function App() {
    const [isPaused, setPause] = useState(false);
    const ws = useRef(null);

    useEffect(() => {
        ws.current = new WebSocket("ws://localhost:8765");
        ws.current.onopen = () => console.log("ws opened");
        ws.current.onclose = () => console.log("ws closed");

        const wsCurrent = ws.current;

        return () => {
            wsCurrent.close();
        };
    }, []);

    useEffect(() => {
        if (!ws.current) return;

        ws.current.onmessage = e => {
            if (isPaused) return;
            const message = e.data;
            console.log(message);
        };
    }, [isPaused]);

    return (
        <div>
            <button onClick={() => setPause(!isPaused)}>
                {isPaused ? "Resume" : "Pause"}
            </button>
        </div>
    );
}


export default App;

ws_client.py

import asyncio
import websockets

async def hello():
    uri = "ws://localhost:8765"
    async with websockets.connect(uri, ping_interval=None) as websocket:
        while True:
            data = await websocket.recv()
            print(f"pushed from server: {data}")

asyncio.get_event_loop().run_until_complete(hello())

ws_server.py

import asyncio
import websockets
import praw
import os

reddit = praw.Reddit(
    client_id=os.environ['REDDIT_ID'],
    client_secret=os.environ['REDDIT_SECRET'],
    password=os.environ['REDDIT_PASS'],
    user_agent="this is me testing praw",
    username="vsaraph"
)

subreddit = reddit.subreddit("news")

async def hello(websocket, path):
    for comment in subreddit.stream.comments(skip_existing=True):
        await websocket.send(comment.body)

start_server = websockets.serve(hello, "localhost", 8765, ping_interval=None)

asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()