Cannot connect server to client in node.js - node.js

Question

I'm trying to connect my client to my server using socket.io to connect them. However it doén't seem to work since i don't get the socket.id in my terminal and i get this error Cannot GET / in my localhost. Please help me to fix it. Thank you so much!
client:
App.js:
import "./App.css";
import io from "socket.io-client";
const socket = io.connect("http://localhost:3000");
function App() {
return <div className="App"></div>;
}
export default App;
package.json:
{
"name": "client",
"version": "0.1.0",
"private": true,
"dependencies": {
"#testing-library/jest-dom": "^5.16.1",
"#testing-library/react": "^12.1.2",
"#testing-library/user-event": "^13.5.0",
"react": "^17.0.2",
"react-dom": "^17.0.2",
"react-scripts": "5.0.0",
"socket.io-client": "^4.4.0",
"web-vitals": "^2.1.2"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": [
"react-app",
"react-app/jest"
]
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
}
}
server:
index.js:
const express = require("express");
const app = express();
const http = require("http");
const cors = require("cors");
const {
Server
} = require("socket.io");
app.use(cors());
const server = http.createServer(app);
const io = new Server(server, {
cors: {
origin: "http://localhost:3000",
methods: ["GET", "POST"],
},
});
io.on("connection", (socket) => {
console.log(`User connected: ${socket.id}`);
socket.on("disconnect", () => {
console.log("User Disconnected", socket.id);
});
})
server.listen(3000, () => {
console.log("SERVER RUNNING");
});
package.json:
{
"name": "server",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "nodemon index.js"
},
"author": "",
"license": "ISC",
"dependencies": {
"connect": "^3.7.0",
"cors": "^2.8.5",
"express": "^4.17.2",
"nodemon": "^2.0.15",
"socket.io": "^4.4.0"
}
}

Answer 1

For this example, the working code for the socket.io
let express = require('express');
let app = express();
let server = require('http').createServer(app);
let io = require('socket.io')(server, {
cors: {
origin: "*",
methods: ["GET", "POST"],
credentials: true
}
})