socket.io官網中使用express實現了一個最簡單的IM即時聊天，今天我們使用koa來實現一下
### 框架準備
1.確保你本地已經安裝好了nodejs和npm，使用koa要求node版本>7.6
2.在你需要的位置新建一個文件夾（官網的簡單命名為chat-example）
3.進入項目目錄，創建package.json文件：
{ "name": "socket-chat-example", "version": "0.0.1", "description": "my first socket.io app", "dependencies": {}}4.命令行中使用npm安裝，執行以下命令
npm install --save koa koa-router http fs socket.io
### 接下來直接上代碼
項目目錄下直接新建index.js
var Koa = require('koa');var app = new Koa();const Router = require('koa-router');const fs = require('fs');const server = require('http').createServer(app.callback());const io = require('socket.io')(server);// 首頁路由let router = new Router();router.get('/', ctx => { ctx.response.type = 'html'; ctx.response.body = fs.createReadStream('./index.html');});app.use(router.routes());// socket連接io.on('connection', (socket) => { socket.on('chat message', (msg) => { console.log('message: '+msg); io.emit('chat message', msg); }); socket.on('disconnect', () => { console.log('user disconnected'); });});// 監聽端口server.listen(3000, () => { console.log('listening on *:3000');});重點：
socket的連接方式是先建立server，它的獲取方式不再是：
var http = require('http').Server(app);var io = require('socket.io')(http);而變成了：
const server = require('http').createServer(app.callback());const io = require('socket.io')(server);node8之后，function(){} 可以簡化為 () => {}，寫法上更加的簡潔
頁面index.html
<!doctype html><html> <head> <title>Socket.IO chat</title> <style> * { margin: 0; padding: 0; box-sizing: border-box; } body { font: 13px Helvetica, Arial; } form { background: #000; padding: 3px; position: fixed; bottom: 0; width: 100%; } form input { border: 0; padding: 10px; width: 90%; margin-right: .5%; } form button { width: 9%; background: rgb(130, 224, 255); border: none; padding: 10px; } #messages { list-style-type: none; margin: 0; padding: 0; } #messages li { padding: 5px 10px; } #messages li:nth-child(odd) { background: #eee; } </style> </head> <body> <ul id="messages"></ul> <form action=""> <input id="m" autocomplete="off" /><button>Send</button> </form> <script src="/socket.io/socket.io.js"></script> <script src="https://code.jquery.com/jquery-1.11.1.js"></script> <script> $(function () { var socket = io(); $('form').submit(function(){ socket.emit('chat message', $('#m').val()); $('#m').val(''); return false; }); socket.on('chat message', function(msg){ $('#message').append($('<li>').text(msg)); }); }); </script> </body></html>
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