Socket.io TypeError: socket is not a function

//module declaration
const express = require("express"),
  bd = require("body-parser"),
  cors = require("cors"),
  http = require("http");
const app = express();
const server = http.createServer(app);
const socket = require("socket.io")(server);

//middleware
const corsOptions = {
  credentials: true,
  origin: ["*"],
};
app.use(bd.json());
app.use(bd.urlencoded({ extended: true }));
app.use(cors(corsOptions));

//io declaration
const io = socket(
  server.listen(5050, (err) => {
    if (err) throw err;
    else console.log("successfully connected");
  })
);

//routing
app.get("/", (req, res) => {
  res.sendFile(__dirname + "/index.html");
});

//websocket configuration
io.on("connection", (socket) => {
  console.log("succesfully connected", socket.id);
  socket.on("btn", (data) => {
    io.socket.emit("btn", data);
    console.log(data);
  });
});

I used require("socket.io)(server) method but this method seems to arising a problem. When I run the app.js, it says socket is not a function.

I tried using websocket for communication between client side and server side. Now I am simply trying to detect a keypress from html in node js but when I use require("socket.io")(server) socket is a function problem arises.

require("socket.io") indeed does not return a function - you're probably looking for the Server class under it, that should be instantiated with new:

const socket = new require("socket.io").Server(server);