FTP获取文件名是报‘数据连接关闭，传输中止’异常 付上代码了

Question

        
        /// <summary>
        /// 接收和发送数据的缓冲区
        /// </summary>
        private static int BLOCK_SIZE = 3072;
        Byte[] buffer = new Byte[BLOCK_SIZE];        /// 获得文件列表
        /// </summary>
        /// <param name="strMask">文件名的匹配字符串</param>
        /// <returns></returns>
        public string[] Dir(string strMask)
        {
            // 建立链接
            if (!bConnected)
            {
                Connect();
            } //建立进行数据连接的socket
            Socket socketData = CreateDataSocket();            //传送命令
            SendCommand("NLST " + strMask); //分析应答代码
            if (!(iReplyCode == 150 || iReplyCode == 125 || iReplyCode == 226))
            {
                throw new IOException(strReply.Substring(4));
            } //获得结果
            strMsg = "";
            while (true)
            {
                int iBytes = socketData.Receive(buffer, buffer.Length, 0);
                //strMsg += ASCII.GetString(buffer, 0, iBytes); 
                strMsg+=Encoding.GetEncoding("gb2312").GetString(buffer, 0, iBytes);
                if (iBytes == buffer.Length || iBytes<buffer.Length)
                {
                    break;
                }
            }
            string[] seperator = { "\r\n" };
            string[] strsFileList = strMsg.Split(seperator, StringSplitOptions.RemoveEmptyEntries);
            socketData.Close();//数据socket关闭时也会有返回码
            if (iReplyCode != 226)
            {
                ReadReply();
                if (iReplyCode != 226)
                {
                    throw new IOException(strReply.Substring(4));
                }
            }
            return strsFileList;
        }        /// 建立进行数据连接的socket
        /// </summary>
        /// <returns>数据连接socket</returns>
        private Socket CreateDataSocket()
        {
            SendCommand("PASV");//PASV
            if (iReplyCode != 227)
            {
                throw new IOException(strReply.Substring(4));
            }
            int index1 = strReply.IndexOf('(');
            int index2 = strReply.IndexOf(')');
            string ipData =
            strReply.Substring(index1 + 1, index2 - index1 - 1);
            int[] parts = new int[6];
            int len = ipData.Length;
            int partCount = 0;
            string buf = "";
            for (int i = 0; i < len && partCount <= 6; i++)
            {
                char ch = Char.Parse(ipData.Substring(i, 1));
                if (Char.IsDigit(ch))
                    buf += ch;
                else if (ch != ',')
                {
                    throw new IOException("Malformed PASV strReply: " +
                    strReply);
                }
                if (ch == ',' || i + 1 == len)
                {
                    try
                    {
                        parts[partCount++] = Int32.Parse(buf);
                        buf = "";
                    }
                    catch (Exception)
                    {
                        throw new IOException("Malformed PASV strReply: " +
                        strReply);
                    }
                }
            }
            string ipAddress = parts[0] + "." + parts[1] + "." +
            parts[2] + "." + parts[3];
            int port = (parts[4] << 8) + parts[5];
            Socket s = new
            Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            IPEndPoint ep = new
            IPEndPoint(IPAddress.Parse(ipAddress), port);
            try
            {
                s.Connect(ep);
            }
            catch (Exception)
            {
                throw new IOException("Can't connect to remote server");
            }
            return s;
        }         /// <summary>
        /// 发送命令并获取应答码和最后一行应答字符串
        /// </summary>
        /// <param name="strCommand">命令</param>
        private void SendCommand(String strCommand)
        {
            //Byte[] cmdBytes =
            // Encoding.ASCII.GetBytes((strCommand + "\r\n").ToCharArray());
            byte[] cmdBytes = Encoding.GetEncoding("gb2312").GetBytes((strCommand + "\r\n").ToCharArray());
            socketControl.Send(cmdBytes, cmdBytes.Length, 0);
            ReadReply();
        }
        /// <summary>
        /// 将一行应答字符串记录在strReply和strMsg
        /// 应答码记录在iReplyCode
        /// </summary>
        private void ReadReply()
        {
            strMsg = "";
            strReply = ReadLine();
            iReplyCode = Int32.Parse(strReply.Substring(0, 3));
        } 
        /// <summary>
        /// 下载一批文件
        /// </summary>
        /// <param name="strFileNameMask">路径名+文件名的匹配字符串</param>
        /// <param name="strFolder">本地目录(不得以\结束)</param>
        public void Get(string strFileNameMask, string strFolder)
        {
            if (!bConnected)
            {
                Connect();
            }
            //获取文件目录
            string[] strFiles = Dir(strFileNameMask);
            OracleDataReader odr = null;
            OracleCommand com = null;
            OracleConnection con = DBhelper.getCon();
            con.Open();
            for (int i = 0; i < strFiles.Length ;i++ )
            {
                string sql = "select h.id from hl_DD_relation h  where h.id = '" + strFiles[i] + "'";
                com = new OracleCommand(sql, con);
                odr = com.ExecuteReader();
                if (odr.Read())
                {
                    continue;
                }
                if (!strFiles[i].Equals(""))//一般来说strFiles的最后一个元素可能是空字符串
                {
                    if (strFiles[i].IndexOf(".") < 0)
                        continue;
                    this.InsertDB(strFiles[i]);
                    Get(strFiles[i], strFolder, strFiles[i]);
                    this.updateDB(strFiles[i],DateTime.Now.ToString());
                    if (strFiles[i].IndexOf(".") != -1)
                        this.Delete(strFiles[i]);
                }
                int j = i;
                j++;
                if (j == strFiles.Length-1)
                    break;
            }
            con.Close();
            odr.Close();
            com.Dispose();
        }如果目录下的文件数量大于2000个的话就会报标题的异常'Data connection closed transfer aborted' 但是，我用F11一步步调试的话，上万个文件名都能正常获取，如果调用Dir(即批量下载里面调用)方法用F10跳过的话就会报这个异常！这是为什么啊~