What's wrong with socket.io?

Question

Node.js

const express = require('express')
const app = express()
const io = require('socket.io')(3000)

app.get('/', (request, response) => {
  response.sendFile(__dirname + '/index.html')
})

io.on('connection', socket => {
  console.log('A user connected!')

  socket.on('disconnect', () => {
    console.log('A user disconnected!')
  })
})

app.listen(3000, () => {
  console.log('Сервер запущен на порте: 3000')
})
// Error: listen EADDRINUSE: address already in use :::3000

Answer 1

Port 3000 is already busy. Use another.

Answer 2

Read here .