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I asked this question earlier about websockets in sanic. This is a follow up.
The following establishes a websocket connection and console.log()s the 'data' message exactly one time:
from sanic import Sanic, response
from sanic.websocket import WebSocketProtocol
import asyncio
import time
app = Sanic()
@app.websocket('/feed')
async def feed(request, ws):
while True:
now = time.time()
data = 'messsage'
print(data)
await ws.send(data)
await asyncio.sleep(1)
@app.route('/')
async def handle_request(request):
return response.html("""
<html><head>
<script>
const ws = new WebSocket("ws://" + location.host + '/feed');
ws.onmessage = event => {
console.log(event.data);
}
</script>
</head>
<body><h1>Main</h1></body>
</html>
""")
app.run(host="0.0.0.0", port=8000)
On the server side, "messsage" is printed periodically. But on the client side, it is console.logged only one time.
server:
client:
It is not clear to me why it prints only once, and not every second like the server side.
However, here are two conditions that /do/ make it print every second.
First, console.log(event), then console.log(event.data) logs periodically, correctly.
@app.route('/')
async def handle_request(request):
return response.html("""
<html><head>
<script>
const ws = new WebSocket("ws://" + location.host + '/feed');
ws.onmessage = event => {
console.log(event); // THIS IS THE ONLY CHANGE
console.log(event.data);
}
</script>
</head>
<body><h1>Main</h1></body>
</html>
""")
That prints this on the client side:
Second, I can keep the javascript as the original,
ws.onmessage = event => {
console.log(event.data);
}
but use the following message, which changes every time:
@app.websocket('/feed')
async def feed(request, ws):
while True:
now = time.time()
data = f'messsage: {now}' # THIS IS THE ONLY CHANGE
print(data)
await ws.send(data)
await asyncio.sleep(1)
That prints this on the server side:
messsage: 1565664622.570395
messsage: 1565664623.572094
messsage: 1565664624.5735717
messsage: 1565664625.5754132
messsage: 1565664626.5771558
messsage: 1565664627.5785906
And this on the client side:
So, these two seemingly irrelevant things take my websocket which does not log to the client side, and makes it do so. Why is this happening?