Help with emit from flask @app.route #1885

Originn · 2022-09-24T18:16:05Z

Originn
Sep 24, 2022

I have trying to figure out for a while where I have an issue that prevent socketio from emitting inside @app.route both in POST and GET. To make is simpler for now I am asking about GET.

my route where I am trying to emit is in routes.py

@app.route("/", methods=["GET", "POST"])
@login_required
def index():
    if request.method == "POST":
        @copy_current_request_context
        def search():
            try:
                while True:
                    some code.....

        t = kthread.KThread(target=search, name=session["name"])
        thread_dict[t.name]= t
        t.start()
        flash("Activated")
        return render_template("/deactivate.html")
    else:
        socketio.emit('func', "Driver connected", broadcast=True)
        return render_template("/index.html")

I have also on routes.py the following

@socketio.on('connect')
def connect():
  join_room(session['user_id'])
  emit("func", "acknowledgment")

on my layout.html I have the following

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.0.1/socket.io.js" integrity="sha512-q/dWJ3kcmjBLU4Qc47E4A9kTB4m3wuTY7vkFJDTZKjTs8jhyGQnaUrxa0Ytd0ssMZhbNua9hE+E7Qv1j+DyZwA==" crossorigin="anonymous"></script>
      <script type="text/javascript" charset="utf-8">
        var socket = io();

        socket.on('connect', function() {
            socket.emit('message', {data: 'I\'m connected!'})
        });
        socket.on('func', function(message) {
            console.log(message);
        });
      </script>

I am initiating socketio in init.py

from flask import Flask
from flask_session import Session
from flask_assets import Environment
from flask_socketio import SocketIO

socketio = SocketIO()

def init_app():
    """Construct core Flask application."""
    app = Flask(__name__, instance_relative_config=False, static_folder='static')
    socketio.init_app(app, manage_session=False, cors_allowed_origins="*", async_mode='eventlet', engineio_logger=True)
    app.config.from_object('config.Config')
    assets = Environment()
    assets.init_app(app)
    with app.app_context():
        # Import parts of our core Flask app
        from . import routes
        from .assets import compile_static_assets

        compile_static_assets(assets)

        return app

wsgi.py file

from application import init_app, socketio, random
from flask import request

app = init_app()

app.secret_key = random
@app.after_request
def after_request(response):
    response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
    response.headers["Expires"] = 0
    response.headers["Pragma"] = "no-cache"
    return response

ssl_cert = "crt.pem"
ssl_key = "key.pem"
    
if __name__ == "__main__":
  socketio.run(app, host='0.0.0.0', port=443, keyfile = ssl_key, certfile=ssl_cert, debug=True)

logs

(10688) wsgi starting up on https://0.0.0.0:443
(10688) accepted ('77.137.194.81', 1030)
-tmu2yMajJlcecgQAAAA: Sending packet OPEN data {'sid': '-tmu2yMajJlcecgQAAAA', 'upgrades': ['websocket'], 'pingTimeout': 20000, 'pingInterval': 25000}
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODmim_Q HTTP/1.1" 200 278 0.000000
-tmu2yMajJlcecgQAAAA: Received packet MESSAGE data 0
-tmu2yMajJlcecgQAAAA: Sending packet MESSAGE data 2["func","acknowledgment"]
-tmu2yMajJlcecgQAAAA: Sending packet MESSAGE data 0{"sid":"5znF3u6I0i2U2BSSAAAB"}
77.137.194.81 - - [24/Sep/2022 18:12:08] "POST /socket.io/?EIO=4&transport=polling&t=ODminpm&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 218 0.000000
(10688) accepted ('77.137.194.81', 1052)
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODminpp&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 241 0.000000
(10688) accepted ('77.137.194.81', 1057)
(10688) accepted ('77.137.194.81', 1060)
-tmu2yMajJlcecgQAAAA: Received request to upgrade to websocket
-tmu2yMajJlcecgQAAAA: Received packet MESSAGE data 2["message",{"data":"I'm connected!"}]
77.137.194.81 - - [24/Sep/2022 18:12:08] "POST /socket.io/?EIO=4&transport=polling&t=ODminsF&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 218 0.000000
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODminsH&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 181 0.000000
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODmintV&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 181 0.000000
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODminui&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 181 0.000000
77.137.194.81 - - [24/Sep/2022 18:12:08] "GET /socket.io/?EIO=4&transport=polling&t=ODminvu&sid=-tmu2yMajJlcecgQAAAA HTTP/1.1" 200 181 0.000000
-tmu2yMajJlcecgQAAAA: Upgrade to websocket successful

As can see from the logs the other emits do work, but why when trying to do socketio.emit('func', "Driver connected", broadcast=True) within GET method there is no data emit/send?

miguelgrinberg · 2022-09-24T18:44:05Z

miguelgrinberg
Sep 24, 2022
Maintainer

Not sure if I'm missing something, but your log does not show any requests that were made to /, so why do you expect the emit to work if the route has not been invoked by the client?

0 replies

Originn · 2022-09-25T07:50:49Z

Originn
Sep 25, 2022
Author

Yes you are correct as I was copying the logs on the restart of the server, but also when "/" is invoked by the client the results are the same.

The logs where "/" is invoked

77.137.194.81 - - [25/Sep/2022 07:44:58] "GET / HTTP/1.1" 200 6627 0.055579
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /static/styles.css HTTP/1.1" 200 2606 0.050378
qbU5Q0eg5bnZd_NfAAAE: Sending packet OPEN data {'sid': 'qbU5Q0eg5bnZd_NfAAAE', 'upgrades': ['websocket'], 'pingTimeout': 20000, 'pingInterval': 25000}
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqnn HTTP/1.1" 200 278 0.001004
htaT1qNNTbHUQhbiAAAF: Sending packet OPEN data {'sid': 'htaT1qNNTbHUQhbiAAAF', 'upgrades': ['websocket'], 'pingTimeout': 20000, 'pingInterval': 25000}
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqo3 HTTP/1.1" 200 278 0.001003
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /static/futurama.png HTTP/1.1" 200 1901 0.003997
qbU5Q0eg5bnZd_NfAAAE: Received packet MESSAGE data 0
qbU5Q0eg5bnZd_NfAAAE: Sending packet MESSAGE data 0{"sid":"h8ELnibP2IpBC-RBAAAG"}
77.137.194.81 - - [25/Sep/2022 07:44:58] "POST /socket.io/?EIO=4&transport=polling&t=ODpcqow&sid=qbU5Q0eg5bnZd_NfAAAE HTTP/1.1" 200 218 0.001001
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqoy&sid=qbU5Q0eg5bnZd_NfAAAE HTTP/1.1" 200 213 0.000000
htaT1qNNTbHUQhbiAAAF: Received packet MESSAGE data 0
htaT1qNNTbHUQhbiAAAF: Sending packet MESSAGE data 0{"sid":"5ze5UTQf0aemYiS5AAAH"}
77.137.194.81 - - [25/Sep/2022 07:44:58] "POST /socket.io/?EIO=4&transport=polling&t=ODpcqpB&sid=htaT1qNNTbHUQhbiAAAF HTTP/1.1" 200 218 0.001003
77.137.194.81 - - [25/Sep/2022 07:44:58] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqpC&sid=htaT1qNNTbHUQhbiAAAF HTTP/1.1" 200 213 0.000000
(2452) accepted ('77.137.194.81', 1079)
htaT1qNNTbHUQhbiAAAF: Received packet MESSAGE data 2["message",{"data":"I'm connected!"}]
77.137.194.81 - - [25/Sep/2022 07:44:58] "POST /socket.io/?EIO=4&transport=polling&t=ODpcqqh&sid=htaT1qNNTbHUQhbiAAAF HTTP/1.1" 200 218 0.001012
qbU5Q0eg5bnZd_NfAAAE: Received request to upgrade to websocket
77.137.194.81 - - [25/Sep/2022 07:44:59] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqqe&sid=qbU5Q0eg5bnZd_NfAAAE HTTP/1.1" 200 181 0.217211
qbU5Q0eg5bnZd_NfAAAE: Upgrade to websocket successful
(2452) accepted ('77.137.194.81', 1082)
htaT1qNNTbHUQhbiAAAF: Received request to upgrade to websocket
77.137.194.81 - - [25/Sep/2022 07:44:59] "GET /socket.io/?EIO=4&transport=polling&t=ODpcqqi&sid=htaT1qNNTbHUQhbiAAAF HTTP/1.1" 200 181 0.562078

7 replies

miguelgrinberg Sep 25, 2022
Maintainer

No, you are looking at this the wrong way. The connection is established by the client, it does not happen in the server. Your main route issues an emit, then returns an HTML template that includes the code for the client to make a Socket.IO connection. Do you see the problem there? This route can only emit to other clients that are already connected, it cannot emit to the client that is about to connect.

Originn Sep 25, 2022
Author

I see. When I am logged in as the same user on two different browsers, then it will emit ["func","Driver connected"]. I was trying different setups but couldn't manage to make in work normally. Do you have any suggestions to me?

miguelgrinberg Sep 25, 2022
Maintainer

then it will emit ["func","Driver connected"]

No. The emit works every time. The client you want to reach isn't connected at the time the emit is issued.

Do you have any suggestions to me?

I'm not sure what more I can do. I have explained the problem. Now you need to redesign the flow of your application so that the user connects to Socket.IO, and only then your server starts emitting to this user.

mhanuel26 Sep 25, 2022

@Originn might worth to know what are you trying to achieve as @miguelgrinberg said, this is not a correct flow for a socket.io application. You can certainly do that with other clients that does not require to access / but in any case a connection should be made first. You would then need to keep sid value to emit in out of context.

Originn Sep 28, 2022
Author

Thanks for your help @mhanuel26 and @miguelgrinberg

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