wshayes/demo.py

## demo.py
# From https://github.com/tiangolo/fastapi/issues/258

from typing import List

from fastapi import FastAPI
from starlette.responses import HTMLResponse
from starlette.websockets import WebSocket, WebSocketDisconnect


app = FastAPI()

html = """
<!DOCTYPE html>
<html>
    <head>
        <title>Chat</title>
    </head>
    <body>
        <h1>WebSocket Chat</h1>
        <form action="" onsubmit="sendMessage(event)">
            <input type="text" id="messageText" autocomplete="off"/>
            <button>Send</button>
        </form>
        <ul id='messages'>
        </ul>
        <script>
            var ws = new WebSocket("ws://localhost:8000/ws");
            ws.onmessage = function(event) {
                var messages = document.getElementById('messages')
                var message = document.createElement('li')
                var content = document.createTextNode(event.data)
                message.appendChild(content)
                messages.appendChild(message)
            };
            function sendMessage(event) {
                var input = document.getElementById("messageText")
                ws.send(input.value)
                input.value = ''
                event.preventDefault()
            }
        </script>
    </body>
</html>
"""


@app.get("/")
async def get():
    return HTMLResponse(html)


class Notifier:
    def __init__(self):
        self.connections: List[WebSocket] = []
        self.generator = self.get_notification_generator()

    async def get_notification_generator(self):
        while True:
            message = yield
            await self._notify(message)

    async def push(self, msg: str):
        await self.generator.asend(msg)

    async def connect(self, websocket: WebSocket):
        await websocket.accept()
        self.connections.append(websocket)

    def remove(self, websocket: WebSocket):
        self.connections.remove(websocket)

    async def _notify(self, message: str):
        living_connections = []
        while len(self.connections) > 0:
            # Looping like this is necessary in case a disconnection is handled
            # during await websocket.send_text(message)
            websocket = self.connections.pop()
            await websocket.send_text(message)
            living_connections.append(websocket)
        self.connections = living_connections


notifier = Notifier()


@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await notifier.connect(websocket)
    try:
        while True:
            data = await websocket.receive_text()
            await websocket.send_text(f"Message text was: {data}")
    except WebSocketDisconnect:
        notifier.remove(websocket)


@app.get("/push/{message}")
async def push_to_connected_websockets(message: str):
    await notifier.push(f"! Push notification: {message} !")


@app.on_event("startup")
async def startup():
    # Prime the push notification generator
    await notifier.generator.asend(None)
If you want to test it out, copy the above to a file main.py and start the server:

uvicorn main:app --reload
Then, open a few tabs at http://localhost:8000/ and send some chat messages (this should work the same as the base tutorial app). Then open http://localhost:8000/push/hello%20world and you should receive a push notification in each of your open tabs showing the message hello world.
	# From https://github.com/tiangolo/fastapi/issues/258

	from typing import List

	from fastapi import FastAPI
	from starlette.responses import HTMLResponse
	from starlette.websockets import WebSocket, WebSocketDisconnect


	app = FastAPI()

	html = """
	<!DOCTYPE html>
	<html>
	<head>
	<title>Chat</title>
	</head>
	<body>
	<h1>WebSocket Chat</h1>
	<form action="" onsubmit="sendMessage(event)">
	<input type="text" id="messageText" autocomplete="off"/>
	<button>Send</button>
	</form>
	<ul id='messages'>
	</ul>
	<script>
	var ws = new WebSocket("ws://localhost:8000/ws");
	ws.onmessage = function(event) {
	var messages = document.getElementById('messages')
	var message = document.createElement('li')
	var content = document.createTextNode(event.data)
	message.appendChild(content)
	messages.appendChild(message)
	};
	function sendMessage(event) {
	var input = document.getElementById("messageText")
	ws.send(input.value)
	input.value = ''
	event.preventDefault()
	}
	</script>
	</body>
	</html>
	"""


	@app.get("/")
	async def get():
	return HTMLResponse(html)


	class Notifier:
	def __init__(self):
	self.connections: List[WebSocket] = []
	self.generator = self.get_notification_generator()

	async def get_notification_generator(self):
	while True:
	message = yield
	await self._notify(message)

	async def push(self, msg: str):
	await self.generator.asend(msg)

	async def connect(self, websocket: WebSocket):
	await websocket.accept()
	self.connections.append(websocket)

	def remove(self, websocket: WebSocket):
	self.connections.remove(websocket)

	async def _notify(self, message: str):
	living_connections = []
	while len(self.connections) > 0:
	# Looping like this is necessary in case a disconnection is handled
	# during await websocket.send_text(message)
	websocket = self.connections.pop()
	await websocket.send_text(message)
	living_connections.append(websocket)
	self.connections = living_connections


	notifier = Notifier()


	@app.websocket("/ws")
	async def websocket_endpoint(websocket: WebSocket):
	await notifier.connect(websocket)
	try:
	while True:
	data = await websocket.receive_text()
	await websocket.send_text(f"Message text was: {data}")
	except WebSocketDisconnect:
	notifier.remove(websocket)


	@app.get("/push/{message}")
	async def push_to_connected_websockets(message: str):
	await notifier.push(f"! Push notification: {message} !")


	@app.on_event("startup")
	async def startup():
	# Prime the push notification generator
	await notifier.generator.asend(None)
	If you want to test it out, copy the above to a file main.py and start the server:

	uvicorn main:app --reload
	Then, open a few tabs at http://localhost:8000/ and send some chat messages (this should work the same as the base tutorial app). Then open http://localhost:8000/push/hello%20world and you should receive a push notification in each of your open tabs showing the message hello world.