socket.io

var server = http.createServer(app);
var io = require('socket.io')(server);

//可以把 发送人数组lists以文件储存  
//one=true 第一次发送    one=false 已经发送过一次
var lists=[{uid:1,one:true},{uid:2,one:false}]

io.on('connection', function (socket) { 
	console.log('连接了') 
	//先接收用户id
    socket.on('uid', function (data) {  
      console.log(data.uid); 
      lists.forEach(function(item){
	      if(item.uid==data.uid&&item.one==true){
	      	//改变发送状态
	      	item.one=false
	      	socket.emit('news', { hello: 'world' });	      	
	      }else if(item.one==false){
	      	console.log('发送过了')
	      }       	
      })          
    });  
});  

　　

<script src= '/socket.io/socket.io.js'></script> 

<script>
  var socket = io('http://localhost:3000');
  	  socket.emit('uid', { uid: '2' });
      socket.on('news', function (data) {               
        alert(data.hello)
      });  
</script>