Flask-SocketIO客户端连接持续报400 Bad Request错误求助

实现前后端WebSocket通信，参考网上示例代码运行时，客户端连接服务器持续抛出400 Bad Request错误。以下是相关代码及错误信息：

Flask服务端代码 #

from flask import Flask, render_template
from flask_socketio import SocketIO, emit


app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret_key'

socketio = SocketIO()
socketio.init_app(app, cors_allowed_origins='*')

name_space = '/dcenter'


@app.route('/')
def index():
    return render_template('index.html')


@app.route('/push')
def push_once():
    event_name = 'dcenter'
    broadcasted_data = {'data': "test message!"}
    socketio.emit(event_name, broadcasted_data, broadcast=False, namespace=name_space)
    return 'done!'


@socketio.on('connect', namespace=name_space)
def connected_msg():
    print('client connected.')


@socketio.on('disconnect', namespace=name_space)
def disconnect_msg():
    print('client disconnected.')


@socketio.on('my_event', namespace=name_space)
def mtest_message(message):
    print(message)
    emit('my_response',
         {'data': message['data'], 'count': 1})


if __name__ == '__main__':

    socketio.run(app, host='0.0.0.0', port=5000, debug=True)

前端客户端代码 #

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>SocketIO Demo</title>
    <script type="text/javascript" src="//cdn.bootcss.com/jquery/3.1.1/jquery.min.js"></script>
    <script type="text/javascript" src="//cdn.bootcss.com/socket.io/1.5.1/socket.io.min.js"></script>
</head>
<body>

<h2>Demo of SocketIO</h2>
<div id="t"></div>
<script>
$(document).ready(function () {
    namespace = '/dcenter';
    var socket = io.connect(location.protocol + '//' + document.domain + ':' + location.port + namespace);
    socket.on('dcenter', function (res) {
        var t = res.data;
        if (t) {
            $("#t").append(t).append('<br/>');
        }

    });
});
</script>
</body>
</html>

错误信息 #

"GET /socket.io/?EIO=3&transport=polling&t=OQIAKtK HTTP/1.1" 400

已尝试更换Flask-SocketIO和engine-io的版本，也更换过其他示例代码，但问题未解决，寻求帮助。

内容的提问来源于stack exchange，提问作者YiJun Sachs