Node.js 尝试通过socketio将php连接到节点服务器

我正试图借助socket.io将PHP文件连接到Heroku上托管的节点服务器。但我无法正确连接它们，Heroku给了我这个错误：

我想不出问题出在哪里

这是客户端代码：

<script>
    var socket = io.connect("https://quiz-5478.herokuapp.com/");

    socket.on("connect", function(data) {
        socket.emit("host__joined", quiz__pin);
    });
    </script>

const express = require("express");
const app = express();
const server = require("http").createServer(app);
const dotenv = require('dotenv');
dotenv.config();

var io = require("socket.io")(server);
var conn = require("./db_connection.js");

app.use(express.static(__dirname + "/node_modules"));

io.on("connection", function (client) {
  console.log("User Connected...");
});

const PORT = process.env.PORT || 5001;
app.listen(PORT, () => console.log(`Server is listening on port ${PORT}...`));

const express = require("express");
const app = express();
const server = require("http").createServer(app);
const dotenv = require('dotenv');
dotenv.config();

var io = require("socket.io")(server);
var conn = require("./db_connection.js");

app.use(express.static(__dirname + "/node_modules"));

io.on("connection", function (client) {
  console.log("User Connected...");
});

const PORT = process.env.PORT || 5001;
app.listen(PORT, () => console.log(`Server is listening on port ${PORT}...`));