Detect when Websocket is disconnected, with Python Bottle / gevent-websocket

Question

I'm using the gevent-websocket module with Bottle Python framework.

When a client closes the browser, this code

$(window).on('beforeunload', function() { ws.close(); });

helps to close the websocket connection properly.

But if the client's network connection is interrupted, no "close" information can be sent to the server.

Then, often, even 1 minute later, the server still believes the client is connected, and the websocket is still open on the server.

Question: How to detect properly that a websocket is closed because the client is disconnected from network?

Is there a websocket KeepAlive feature available in Python/Bottle/gevent-websocket?

One answer from Web Socket: cannot detect client connection on internet disconnect suggests to use a heartbeat/ping packet every x seconds to tell the server "I'm still alive". The other answer suggests using a setKeepAlive(true). feature. Would this feature be available in gevent-websocket?

Example server code, taken from here:

from bottle import get, template, run
from bottle.ext.websocket import GeventWebSocketServer
from bottle.ext.websocket import websocket

users = set()

@get('/')
def index():
    return template('index')

@get('/websocket', apply=[websocket])
def chat(ws):
    users.add(ws)
    while True:
        msg = ws.receive()
        if msg is not None:
            for u in users:
                u.send(msg)
        else:
            break
    users.remove(ws)

run(host='127.0.0.1', port=8080, server=GeventWebSocketServer)

eatmeimadanish eatmeimadanish · Accepted Answer · 2018-03-23T19:44:43

First you need to add a timeout to the receive() method.

with gevent.Timeout(1.0, False):
    msg = ws.receive()

Then the loop will not block, if you send even an empty packet and the client doesn't respond, WebsocketError will be thrown and you can close the socket.

Detect when Websocket is disconnected, with Python Bottle / gevent-websocket

1 Answers