Error while uploading the socket io chat app

Error is :-Access to XMLHttpRequest at 'https://lets-talk-orcin.vercel.app/socket.io/?EIO=4&transport=polling&t=OwKav8O&sid=Qge6bm6DZTQlvvJBAAAA' from origin 'https://lets-talk-frontend.vercel.app' has been blocked by CORS policy:No 'Access-Control-Allow-Origin' header is present on the requested resource.I have created a chat app using nodejs and reactjs. On my local machine it works perfectly but after deploying on vercel it gives above error.please help me to solve this.

My server side code to connect with socket io is

app.use(    cors({        origin: process.env.FRONTEND_URL,        credentials: true,    }))const server = app.listen(PORT, () => {    console.log("Listening at port no. ", PORT);});// Frontend url is :- https://lets-chat-frontend.vercel.appconst io = require('socket.io')(server, {    cors: {        origin: process.env.FRONTEND_URL,        methods: ["GET", "POST"],        transports: ['websocket', 'polling'],    },    allowEIO3: true});

My client side code to connect with socket io is

import { io } from "socket.io-client";export const socket = io("https://lets-talk-orcin.vercel.app/", {    autoConnect: false,});