How can i deal with node.js/socket.io memory leak?

What part of this code will cause a memory leak?

I make a process listener.It can listen memory's change.So i know the memory usage is growing and it never fall.Sometimes it can growing to 800,000k and make computer crash.

The number of concurrent connections accepted is about 100-300.

Code like this:

var http = require('http').createServer(),
socketio = require('socket.io').listen(http);
var fs = require("fs");
var util = require('util');

http.listen(3000);
var connectCount = 0;
socketio.on("connection",function(socket){
   connectCount++;
   socket.on('chatMessage',function(msg){
            delete res;
            delete res2;
          //json string for return to client 
            var res = {
                channel:msg.channel,
                clubname:msg.name,
                dn:msg.dn,  .
                mesContent:msg.messageContent,
                dn1:"",
                dn2:""
            }

            var res2 = {
                channel:msg.channel,
                clubname:msg.name,
                dn:"",  
                mesContent:msg.messageContent,
                dn1:"",
                dn2:"" ,
                curChannel:msg.curChannel
            }

            if(msg.channel == 0){   //Public Message

                socket.emit('pubMessage',res2,function(){
                    console.log("ok");
                });
                socket.broadcast.emit('pubMessage',res,function(){
                    console.log("ok");
                });
            }else if(msg.channel == 7){ //Private Message

                socket.emit('priMessage',res,function(){
                    console.log("ok");
                });
                socket.broadcast.emit('priMessage',res,function(){
                    console.log("ok");
                });
            }
        });
        //Cache data geter
        socket.on('getChatCache',function(type){
            var ind = 0;
            socket.emit("getChatCache",type==7 ? chatCache_20.where("channel",type) : chatCache_20);
        });
        //Chat server init method
        socket.on('init',function(){
            socket.emit('init',{chatChache:chatCache_20});
        }); 
       })