异步无法两次连接

        /**//// <summary>
        /// 开始侦听
        /// </summary>
        /// <param name="pDestFold"></param>
        /// <param name="pTempFileFold"></param>
        public void StartListen(string pDestFold,string pTempFileFold)
        {
            this.destFold = pDestFold;
            this.tempFold = pTempFileFold;

            this.ser = new Socket(this.localAddr.AddressFamily,SocketType.Stream,ProtocolType.Tcp);
            IPEndPoint ep = new IPEndPoint(this.localAddr,this.port);
            this.ser.Bind(ep);
            this.ser.Listen(5);
            this.ser.BeginAccept(new AsyncCallback(this.callAccept),this.ser);


            //            System.Threading.Thread th = new System.Threading.Thread(new System.Threading.ThreadStart(this.list));
            //            th.Start();
        }

        private void callAccept(IAsyncResult iar)
        {
            Socket serverMain = (Socket)iar.AsyncState;            
            Socket server = serverMain.EndAccept(iar);
        //    NetworkStream stream = new NetworkStream(server);
        
            byte[] len = new byte[8];

            try
            {
                //先读取8个字节的长度定义
                server.Receive(len,0,8,SocketFlags.None);
                int iLen = BitConverter.ToInt32(len,0);
                    
                //读取命令
                byte [] dataContent = new byte[iLen];
                server.Receive(dataContent,0,dataContent.Length,SocketFlags.None);                
                //收到的命令
                string data = System.Text.Encoding.UTF8.GetString(dataContent);
                Log.AddEvent("Listen",data);

                //分析命令
                string[] cmd = data.Split('|');
                OneSync sync = new OneSync(cmd[0],cmd[1]);
                //目标文件
                string dest = string.Format("{0}\\{1}",this.destFold,sync.FileName);
                //执行操作
                //没有改名，因为考虑目标盘可能没有指定文件，于是将操作化为先在删除目标盘上的原文件，再拷贝源的新文件。
                switch(sync.Method)
                {
                    case Methods.Delete:
                        System.IO.File.Delete(dest);
                        break;
                    case Methods.Copy:    
                            
                        //读取文件长度
                        server.Receive(len,0,8,SocketFlags.None);
                        iLen = BitConverter.ToInt32(len,0);
                        //读取文件内容
                        string temp = string.Format("{0}\\{1}.tmp",this.tempFold,sync.FileName.Replace("\\","_"));
                        System.IO.FileStream file = System.IO.File.OpenWrite(temp);
                        byte [] buffer = new byte[1024];
                        int iRead = iLen;
                        int iLeft = iLen;
                        while(iLeft>0)
                        {
                            if(iLeft>1024)
                                iRead = server.Receive(buffer,0,1024,SocketFlags.None);    
                            else
                                iRead = server.Receive(buffer,0,iLeft,SocketFlags.None);    
                            iLeft = iLeft - iRead;
                            //写入文件
                            file.Write(buffer,0,iRead);
                        }
                        //关闭文件
                        file.Close();
                        //检查目标目录是否存在
                        System.IO.FileInfo info = new System.IO.FileInfo(dest);
                        if(!info.Directory.Exists)
                            info.Directory.Create();//创建目标目录
                        //改名
                        System.IO.File.Copy(temp,dest,true);
                        System.IO.File.Delete(temp);
                    //    System.IO.File.Move(temp,dest);//目标文件存在时出
                        break;
                }
                //回送收到的命令
                Byte[] msg = System.Text.Encoding.ASCII.GetBytes("OK");
                server.Send(msg, 0, msg.Length,SocketFlags.None);
                server.Close();
            }        
            catch(Exception e)
            {
                Log.AddErr("TcpServer", e);
            }
        }