通过.NET代码连接FTP服务器时出现错误代码551

Question

我使用下面的c＃代码连接FTP服务器。有时在发送文件时，它会收到错误代码551和说明：发送FTP时发现异常：远程服务器返回错误：（551）页面类型未知。

我不知道为什么会这样。 谁能告诉我这是什么问题？

private bool sendFTP(string sDestPath, string sFileName, string sUserName, string sPassword, string sDomain, bool isProxyUsed, string sProxy, int nProxyPort, byte[] sData)
       {
           try
           {
               NetworkCredential nCred;
               if (!sDomain.Equals(String.Empty))
               {
                   nCred = new System.Net.NetworkCredential(sUserName, sPassword, sDomain);
               }
               else
               {
                   nCred = new System.Net.NetworkCredential(sUserName, sPassword);
               }
               FtpWebRequest request = (FtpWebRequest)WebRequest.Create(sDestPath + "//" + sFileName);
               request.Method = WebRequestMethods.Ftp.UploadFile;
               request.Credentials = nCred;
               request.Proxy = new WebProxy();
               if (isProxyUsed)
               {
                   WebProxy p = new WebProxy(sProxy, nProxyPort);
                   p.Credentials = nCred;
                   WebRequest.DefaultWebProxy = p;
               }
               request.ContentLength = sData.Length;
               Stream reqStream = request.GetRequestStream();
               reqStream.Write(sData, 0, sData.Length);
               reqStream.Close();
               FtpWebResponse response = (FtpWebResponse)request.GetResponse();
               return true;
           }
           catch (Exception objEx)
           {
               // Error
               EventLog.WriteEntry("STCCommon", "Exception Caught:" + objEx.Message, EventLogEntryType.Error);
               throw new Exception("Exception caught in sending FTP: " + objEx.Message);
           }

       }