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Server IO Emit to Specific Socket

Video Lecture

Server Emit to Specific Socket Server Emit to Specific Socket

Description

Using IO to emit a message to a specific socket ID.

img/server-emit-to-specific.jpg

./src/server/luckyNumbersGame.ts

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export default class LuckyNumbersGame {
  public LuckyNumbers: { [id: string]: number } = {}

  public GetWinners(number: number): string[] {
    const winners = []
    for (let id in this.LuckyNumbers) {
      if (number === this.LuckyNumbers[id]) {
        winners.push(id)
      }
    }
    return winners
  }
}

./src/server/server.ts

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import { createServer } from 'http'
import { Server } from 'socket.io'
import * as express from 'express'
import * as path from 'path'
import LuckyNumbersGame from './luckyNumbersGame'

const port = 3000

const app = express()
app.use(express.static(path.join(__dirname, '../client')))

const server = createServer(app)

const io = new Server(server)

const game = new LuckyNumbersGame()

io.on('connection', (socket) => {
  console.log('a user connected : ' + socket.id)

  game.LuckyNumbers[socket.id] = Math.floor(Math.random() * 20)

  socket.emit('message', 'Hello, your lucky number is ' + game.LuckyNumbers[socket.id])

  socket.broadcast.emit('message', 'Everybody, say hello to ' + socket.id)

  socket.on('disconnect', () => {
    console.log('socket disconnected : ' + socket.id)

    socket.broadcast.emit('message', socket.id + ' has left the building')
  })
})

server.listen(port, () => {
  console.log('Server listening on port ' + port)
})

setInterval(() => {
  const randomNumber = Math.floor(Math.random() * 20)
  const winners = game.GetWinners(randomNumber)
  if (winners.length) {
    winners.forEach((w) => {
      io.to(w).emit('message', '*** You are the winner with ' + randomNumber + ' ***')
    })
  }
  io.emit('message', randomNumber)
}, 1000)

./src/client/client.ts

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import { io } from 'socket.io-client'

const socket = io()

socket.on('connect', () => {
  document.body.innerText = 'Connected : ' + socket.id
})

socket.on('message', (message) => {
  document.body.innerHTML += '<p>' + message + '</p>'
  window.scrollTo({ top: document.body.scrollHeight, behavior: 'smooth' })
})