socket.io实现在线群聊功能

我写的聊天程序：

index.html

<script src="/socket.io/socket.io.js"></script><script>
 var socket = io.connect('http://localhost');
  socket.on("notice", function(data){
    var msg = document.getElementById('all').value;
    document.getElementById('all').innerText = msg + "n" + data.message;
  });
  var chat_fn = function(){
    var msg = document.getElementById("message").value;
    socket.emit("chat", {message: msg});
  };
  socket.on("nickname ready", function(data){
    alert("nickname changed.");
  });
  var change_nickname = function(){
    var nickname = document.getElementById("nickname").value;
    socket.emit('set nickname', nickname);
  };</script><textarea id="all" cols=40 rows=20></textarea><br /><label>Message:</label><input id="message" type="text" name="message" cols=120/><input id="chat_btn" type="button" value="chat" onclick="javascript:chat_fn()" /><label>NickName:</label><input id="nickname" typee="text" name="nickname" /><input id="chang_name" type="button" value="nickname" onclick="javascript:change_nickname()" />
app.js
var app = require('http').createServer(handler)
 , io = require('socket.io').listen(app)
 , fs = require('fs');
app.listen(80);function handler (req, res) {
 fs.readFile(__dirname + '/index.html',
 function (err, data) {
  if (err) {
   res.writeHead(500);
   return res.end('Error loading index.html');
  }
  res.writeHead(200);
  res.end(data);
 });}
io.sockets.on('connection', function (socket) {
 // socket.emit('news', { hello: 'world' });
 // socket.on('my other event', function (data) {
 //  console.log(data);
 // });
 socket.set('nickname', 'nickname', function(){
 });
 socket.on('set nickname', function(name){
  socket.set('nickname', name, function(){
   console.log("change nickname=>" + name);
   socket.emit('nickname ready');
  });
 });
 socket.on('chat', function(data){
  socket.get('nickname', function(err, name){
  socket.emit("notice", {message: name + ":" + data.message});
  socket.broadcast.emit("notice", {message: name + ":" + data.message});
  console.log("chat: " + data.message);
  });
 });});