php客户端连接socket.io在ie下disconnect事件问题

server.js

var app = require('express')()
  , server = require('http').createServer(app)
  , io = require('socket.io').listen(server,{log:false});

server.listen(888);

app.get('/', function (req, res) {
  res.sendfile(__dirname + '/index.html');
});

io.sockets.on('connection', function (socket) {
  console.log('connection '+new Date());
  socket.emit('news', { hello: 'world' });
  socket.on('my other event', function (data) {
    console.log(data);
  });
  socket.on('disconnect', function () {
    console.log('user disconnected '+new Date());
  });
});

express 3.0.6 socket.io 0.9.13

client.html

客户端是apache+php的，在google浏览器一切正常，刷新和关闭都正常 但是在ie和ff能连接上并正常通信，但是在1分钟之内会自动触发disconnect事件，反而正常退出或刷新却不能触发disconnect事件，混乱了...求高手帮忙解答!!!!!