websocket_chat_server.py

import asyncio

import websockets
from websockets.exceptions import ConnectionClosed


connected = set()

async def suppress(f, *, exception):
    try:
        return await f
    except exception:
        pass


async def broadcast(message):
    global connected
    broadcasts = (ws.send(message) for ws in connected)
    broadcasts = [suppress(f, exception=ConnectionClosed) for f in broadcasts]
    await asyncio.wait(broadcasts)


async def handler(websocket, path):
    global connected
    connected.add(websocket)
    while True:
        try:
            message = await websocket.recv()
        except ConnectionClosed:
            connected.remove(websocket)
            break
        else:
            await broadcast(message)


start_server = websockets.serve(handler, 'localhost', 8765)

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