polling-xhr.js:157 POST https://cet-chat.herokuapp.com/socket.io/?EIO=4&transport=polling&t=NsGVGZJ&sid=2I5zXjHN7fUZN5lNAAAA 400 (BAD REQUEST)

[somesh1234567]

``Hi everybody I am trying to build a chat app using flask and socketio
The app is working fine in localserver(PORT: 5000)
but when I deploy it using gunicorn it is throing error
PROCFILE: web: gunicorn -k geventwebsocket.gunicorn.workers.GeventWebSocketWorker -w 1 app:app
app.py:
`import os
from logging import debug
from flask import Flask, render_template, request, redirect, url_for, session
from flask_sqlalchemy import SQLAlchemy
from flask_socketio import SocketIO, join_room, leave_room, emit, rooms
from flask_session import Session

app = Flask(name)
app.debug = True
app.config['SECRET_TYPE'] = os.environ.get('SECRET')
app.config['SQLALCHEMY_DATABASE_URI'] = "sqlite:///chat.db"
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SESSION_TYPE'] = "sqlalchemy"

db = SQLAlchemy(app)
app.config['SESSION_SQLALCHEMY'] = db

Session(app)

socketio = SocketIO(app, manage_session=False)

@app.route("/", methods=['GET', 'POST'])
def hello_world():
return render_template('index.html')

@app.route("/chat", methods=['GET', 'POST'])
def chat():
if request.method == 'POST':
username = request.form['username']
room = request.form['room']
session['username'] = username
session['room'] = room
return render_template('chat.html', session = session)
else:
if(session.get('username') is not None):
return render_template('chat.html', session = session)
else:
return redirect(url_for('index'))

@socketio.on('join', namespace='/chat')
def join(message):
room = session.get('room')
join_room(room)
emit('status', {'msg': session.get('username') + 'has enterted the room.'}, room = room)

@socketio.on('text', namespace='/chat')
def text(message):
room = session.get('room')
emit('message', {'msg': session.get('username') + ' : ' + message['msg']}, room=room)

@socketio.on('left', namespace='/chat')
def left(message):
room = session.get('room')
username = session.get('username')
leave_room(room)
session.clear()
emit('status', {'msg': username + ' has left the room.'}, room=room)

if name == 'main':
app.run()`

chat.html:
`

<title>Chat</title>

<script src="https://code.jquery.com/jquery-3.6.0.min.js"
    integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4=" crossorigin="anonymous">
    </script>
<script type="text/javascript"
    src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.4.0/socket.io.min.js"></script>
<script type="text/javascript">
    var socket;
    $(document).ready(function () {
        socket = io.connect('http://' + document.domain + ':' + location.port + '/chat');
        socket.on('connect', function () {
            socket.emit('join', {});
        });
        socket.on('status', function (data) {
            $('#chat').val($('#chat').val() + '<' + data.msg + '>\n');
            $('#chat').scrollTop($('#chat')[0].scrollHeight);
        });
        socket.on('message', function (data) {
            $('#chat').val($('#chat').val() + data.msg + '\n');
            $('#chat').scrollTop($('#chat')[0].scrollHeight);
        });
        $('#send').click(function (e) {
            text = $('#text').val();
            $('#text').val('');
            socket.emit('text', { msg: text });
        });
    });
    function leave_room() {
        socket.emit('left', {}, function () {
            socket.disconnect();
            // go back to the login page
            window.location.href = "{{ url_for('hello_world') }}";
        });
    }
</script>

CET ChatBox

Room: {{session['room']}}

<textarea id="chat" cols="70" rows="10" placeholder="No messages yet."></textarea>
SEND

Leave

` Any help will be great as to how to solve this issue Requirements.txt: bidict==0.21.4 cachelib==0.4.1 certifi==2021.10.8 cffi==1.15.0 charset-normalizer==2.0.8 click==8.0.3 colorama==0.4.4 dnspython==2.1.0 eventlet==0.33.0 Flask==2.0.2 Flask-Session==0.4.0 Flask-SocketIO==5.1.1 Flask-SQLAlchemy==2.5.1 gevent==21.8.0 gevent-websocket==0.10.1 greenlet==1.1.2 gunicorn==20.1.0 idna==3.3 itsdangerous==2.0.1 Jinja2==3.0.3 MarkupSafe==2.0.1 pycparser==2.21 python-engineio==4.3.0 python-socketio==5.5.0 requests==2.26.0 six==1.16.0 SQLAlchemy==1.4.27 urllib3==1.26.7 Werkzeug==2.0.2 zope.event==4.5.0 zope.interface==5.4.0

[darrachequesne]

Hi! Did you check the scalability notes here: https://python-socketio.readthedocs.io/en/latest/server.html#scalability-notes?