C#实现FTP功能问题，高手请进

Question

我用C#实现FTP功能，已经可以上传下载了，但是有不稳定，当远程FTP服务器的数据量大或网速慢的时候下一会儿就提示如下错误：
   1、“基础连接断开，超时”，
   2、用户代码未处理 System.Net.WebException   Message="远程服务器返回错误: (500) 语法错  误，无法识别命令。"
请问用API是不是要稳定点，我的下载代码如下：
BackgroundWorker bw = sender as BackgroundWorker;
FtpSettings f = e.Argument as FtpSettings;IList<string> vDownFiles =new  List<string>();
string[] temp = GetFileList(f.Host ,f.Port , f.Username , f.Password ,f.TargetFolder , "*.*");
for (int i = 0; i < temp.Length; i++)
{
   vDownFiles.Add(temp[i]);
}foreach (string item in vDownFiles)
{
                if (item.Contains("win2003Hp.iso"))
                {
                    int kk = 10;
                }                FileStream outputStream = new FileStream(@"e:\test\" + item, FileMode.Create);                // set up the host string to request.  this includes the target folder and the target file name (based on the source filename)
                string DownLoadPath = String.Format("{0}/{1}{2}", f.Host, f.TargetFolder == "" ? "" : f.TargetFolder + "/", Path.GetFileName(item));
                if (!DownLoadPath.ToLower().StartsWith("ftp://"))
                    DownLoadPath = "ftp://" + DownLoadPath;
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create(DownLoadPath);
                request.Method = WebRequestMethods.Ftp.DownloadFile;
                request.UseBinary = true;
                request.UsePassive = f.Passive;
                request.Credentials = new NetworkCredential(f.Username, f.Password);                FtpWebResponse response = (FtpWebResponse)request.GetResponse();                Stream ftpStream = response.GetResponseStream();
                long cl = response.ContentLength;
                string FileSizeDescription = GetFileSize(cl);
                //int bufferSize = 2048;
                int readCount;
                long DownLoadBytes = 0;
                int ChunkSize = 4096, NumRetries = 0, MaxRetries = 50;
                byte[] buffer = new byte[ChunkSize];                readCount = ftpStream.Read(buffer, 0, ChunkSize);
                while (readCount > 0)
                {                    //outputStream.Write(buffer, 0, readCount);
                    //readCount = ftpStream.Read(buffer, 0, bufferSize);                    //DownLoadBytes += readCount;                    //// update the user interface
                    //string SummaryText = String.Format("传输完成比率 {0} / {1}", GetFileSize(DownLoadBytes), FileSizeDescription);
                    //bw.ReportProgress((int)(((decimal)DownLoadBytes / (decimal)cl ) * 100), SummaryText);
                    try
                    {
                        if (bw.CancellationPending)
                            return;                        // send this chunk to the server.  it is sent as a byte[] parameter, but the client and server have been configured to encode byte[] using MTOM. 
                        outputStream.Write(buffer, 0, readCount);                        // sentBytes is only updated AFTER a successful send of the bytes. so it would be possible to build in 'retry' code, to resume the upload from the current SentBytes position if AppendChunk fails.
                        DownLoadBytes += readCount;                        // update the user interface
                        string SummaryText = String.Format("传输完成比率 {0} / {1}", GetFileSize(DownLoadBytes), FileSizeDescription);
                        bw.ReportProgress((int)(((double)DownLoadBytes / (double)cl) * 100), SummaryText);
                    }
                    catch (Exception ex)
                    {
                        Debug.WriteLine("Exception: " + ex.ToString());
                        if (NumRetries++ < MaxRetries)
                        {
                            // rewind the filestream and keep trying
                            ftpStream.Position -= DownLoadBytes;
                        }
                        else
                        {
                            throw new Exception(String.Format("Error occurred during upload, too many retries. \n{0}", ex.ToString()));
                        }
                    }
                    readCount = ftpStream.Read(buffer, 0, ChunkSize); // read the next chunk (if it exists) into the buffer.  the while loop will terminate if there is nothing left to read                }                ftpStream.Close();
                outputStream.Close();
                response.Close();
                using (FtpWebResponse responseN = (FtpWebResponse)request.GetResponse())
                    System.Diagnostics.Debug.WriteLine(String.Format("DownLoad File Complete, status {0}", responseN.StatusDescription));}

Answer 1

如果服务器支持，可以使用端点续传增加可靠性。Google: ftpwebrequest 端点续传

Answer 2

首先非常感谢楼上的朋友，但是不够详细，最好有先关的DEMO或关键代码 

Answer 3

FtpWebResponse response = (FtpWebResponse)request.GetResponse();
Stream ftpStream = response.GetResponseStream();
这两句放到try里面去
internal static bool FtpDownloadFile(FtpSite ftpSite) //定义个对象，封装参数
        {
            if (ftpSite == null)
            {
                throw new ArgumentNullException("ftpSite");
            }
            //根据URI创建FtpWebRequest对象
            FtpWebRequest ftpRequest = (FtpWebRequest)FtpWebRequest.Create(ftp.FileUri);
            //ftp用户名和密码
            ftpRequest.Credentials = new NetworkCredential(ftpSite.UserName, ftpSite.Password);
            ftpRequest.Method = WebRequestMethods.Ftp.DownloadFile;     //指定操作类别
            ftpRequest.UseBinary = true;    //指定数据传输类型
            ftpRequest.KeepAlive = false;   //下载完后不用保持连接
            return SaveAsFile(ftpRequest, upgradeReport.SaveFileName);
        }        /// <summary>
        /// 将服务端响应流保存至文件
        /// </summary>
        static bool SaveAsFile(WebRequest request, string saveName)
        {
            WebResponse response = null;
            request.Proxy = null;
            request.Timeout = 60000;    //设置请求超时时间
            //request.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore);
            try
            {
                response = (WebResponse)request.GetResponse();
                using (var responseStream = response.GetResponseStream())
                {
                    using (var fs = new FileStream(saveName, FileMode.Create, FileAccess.ReadWrite, FileShare.Read))
                    {
                        int bufferLength = 2048, offset = 0;
                        byte[] buffer = new byte[bufferLength];
                        while ((offset = responseStream.Read(buffer, 0, bufferLength)) > 0)
                        {
                            fs.Write(buffer, 0, offset);
                        }                        
                    }
                }
                return true;
            }
            catch (Exception exp)
            {
                //handle exp or throw;
                return false;
            }
            finally
            {
                if (response != null) response.Close();
            }
        }

Answer 4

我现在改成如下代码，可以下载的大小比原来提高很多，可是在下载一会儿就提示：远程服务器返回错误: (426) 连接关闭；传输中止。我的代码如下：
    FileStream outputStream = new FileStream(@"e:\test\" + item, FileMode.Create);                // set up the host string to request.  this includes the target folder and the target file name (based on the source filename)
                string DownLoadPath = String.Format("{0}/{1}{2}", f.Host, f.TargetFolder == "" ? "" : f.TargetFolder + "/", Path.GetFileName(item));
                if (!DownLoadPath.ToLower().StartsWith("ftp://"))
                    DownLoadPath = "ftp://" + DownLoadPath;
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create(DownLoadPath);
                request.Method = WebRequestMethods.Ftp.DownloadFile;
                request.UseBinary = true;
                request.UsePassive = f.Passive;
                request.Credentials = new NetworkCredential(f.Username, f.Password);
                request.KeepAlive = true;
                request.ReadWriteTimeout = System.Threading.Timeout.Infinite;
                request.Timeout = System.Threading.Timeout.Infinite;
                request.Proxy = null;
                request.UsePassive = false;                                             FtpWebResponse response = (FtpWebResponse)request.GetResponse();                Stream ftpStream = response.GetResponseStream();
                long cl = response.ContentLength;
                string FileSizeDescription = GetFileSize(cl);
                //int bufferSize = 2048;
                int readCount;
                long DownLoadBytes = 0;
                int ChunkSize = 4096, NumRetries = 0, MaxRetries = 50;
                byte[] buffer = new byte[ChunkSize];                readCount = ftpStream.Read(buffer, 0, ChunkSize);
                while (readCount > 0)
                {                    //outputStream.Write(buffer, 0, readCount);
                    //readCount = ftpStream.Read(buffer, 0, bufferSize);                    //DownLoadBytes += readCount;                    //// update the user interface
                    //string SummaryText = String.Format("传输完成比率 {0} / {1}", GetFileSize(DownLoadBytes), FileSizeDescription);
                    //bw.ReportProgress((int)(((decimal)DownLoadBytes / (decimal)cl ) * 100), SummaryText);
                    try
                    {
                        if (bw.CancellationPending)
                            return;                        // send this chunk to the server.  it is sent as a byte[] parameter, but the client and server have been configured to encode byte[] using MTOM. 
                        outputStream.Write(buffer, 0, readCount);                        // sentBytes is only updated AFTER a successful send of the bytes. so it would be possible to build in 'retry' code, to resume the upload from the current SentBytes position if AppendChunk fails.
                        DownLoadBytes += readCount;                        // update the user interface
                        string SummaryText = String.Format("传输完成比率 {0} / {1}", GetFileSize(DownLoadBytes), FileSizeDescription);
                        bw.ReportProgress((int)(((double)DownLoadBytes / (double)cl) * 100), SummaryText);
                    }
                    catch (Exception ex)
                    {
                        Debug.WriteLine("Exception: " + ex.ToString());
                        if (NumRetries++ < MaxRetries)
                        {
                            // rewind the filestream and keep trying
                            ftpStream.Position -= DownLoadBytes;
                        }
                        else
                        {
                            throw new Exception(String.Format("Error occurred during upload, too many retries. \n{0}", ex.ToString()));
                        }
                    }
                    readCount = ftpStream.Read(buffer, 0, ChunkSize); // read the next chunk (if it exists) into the buffer.  the while loop will terminate if there is nothing left to read                }                ftpStream.Close();
                outputStream.Close();
                response.Close();
                using (FtpWebResponse responseN = (FtpWebResponse)request.GetResponse())
                    System.Diagnostics.Debug.WriteLine(String.Format("DownLoad File Complete, status {0}", responseN.StatusDescription));            }

Answer 5

你可以用 http 协议 进行处理。

Answer 6

那个协议处理无所谓，关键是需要稳定，http协议是不是要稳定些

Answer 7

FtpWebRequest 好像是有这样那样的问题，还是用 socket 写把

Answer 8

自己搞定了代码贴出来供大家参考： /// <summary>
 /// 下载
 /// </summary>
 /// <param name="filePath"></param>
 /// <param name="fileName"></param>
public void Download(string ftpURI, string fPath, string ftpUserID, string ftpPassword, string filePath)
        {           
            this.toolStripProgressBar1.Value = 0;
            using (BackgroundWorker backgroundWorker = new BackgroundWorker())
            {                
                backgroundWorker.WorkerReportsProgress = true;
                backgroundWorker.WorkerSupportsCancellation = true;
                // 异步获取数据
                backgroundWorker.DoWork += new DoWorkEventHandler(delegate(object o, DoWorkEventArgs workerEventArgs)
                {
                    string[] temp = GetFileList(ftpURI, 21, ftpUserID, ftpPassword, fPath, "*.*");                    foreach (string item in temp)
                    {
                        string fileName = item;                        ifComplete = false;                        this.BeginInvoke(new myDelegatDoProcess(doProcess));                        //backgroundWorker.ReportProgress((int)(((double)0.1 / (double)1) * 100), "正在获得文件列表，请稍候..."); System.Threading.Thread.Sleep(1000);                        FtpWebRequest reqFTP;
                        try
                        {
                            //backgroundWorker.ReportProgress((int)(((double)0.75 / (double)1) * 100), "正在下载文件，请稍候..."); System.Threading.Thread.Sleep(1000);                            FileStream outputStream = new FileStream(filePath + "\\" + fileName, FileMode.Create);                            reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("Ftp://" + ftpURI + "/" + fPath + "/" + fileName));
                            reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
                            reqFTP.UseBinary = true;
                            reqFTP.UsePassive = false;
                            reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
                            FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                            Stream ftpStream = response.GetResponseStream();
                            long cl = response.ContentLength;
                            int bufferSize = 2048;
                            int readCount;
                            byte[] buffer = new byte[bufferSize];
                            long DownLoadBytes = 0;
                            string FileSizeDescription = GetFileSize(cl);
                            readCount = ftpStream.Read(buffer, 0, bufferSize);
                            while (readCount > 0)
                            {
                                outputStream.Write(buffer, 0, readCount);
                                readCount = ftpStream.Read(buffer, 0, bufferSize);                                DownLoadBytes += readCount;
                                //this.Text = "文件[" + fileName + "]下载完成" + GetFileSize(DownLoadBytes) + @"/" + FileSizeDescription;
                                //this.Refresh();
                                string SummaryText = String.Format("正在下载文件 {0} 传输完成比率 {1} / {2}",item , GetFileSize(DownLoadBytes), FileSizeDescription);
                                backgroundWorker.ReportProgress((int)(((double)DownLoadBytes / (double)cl) * 100), SummaryText);
                                //this.Refresh();
                                //statusStrip1.Refresh(); 
                            }                            ftpStream.Close();
                            outputStream.Close();
                            response.Close();
                        }
                        catch (Exception ex)
                        {
                            //Insert_Standard_ErrorLog.Insert("FtpWeb", "Download Error --> " + ex.Message);
                        }
                    }                    
                });                backgroundWorker.ProgressChanged += new ProgressChangedEventHandler(delegate(object sender, ProgressChangedEventArgs e)
                {
                    //if (e.UserState != null && e.UserState.ToString() != "") { m_Result = e.UserState.ToString(); }
                    this.toolStripStatusLabel1.Text = e.UserState.ToString(); // the message will be something like: 45 Kb / 102.12 Mb             
                    try
                    {
                        this.toolStripProgressBar1.Value = Math.Min(this.toolStripProgressBar1.Maximum, e.ProgressPercentage);
                    }
                    catch { }
                    this.statusStrip1.Refresh();
                });                backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object o, RunWorkerCompletedEventArgs x)
                {
                    string SummaryText = String.Format("下载完成");
                    backgroundWorker.ReportProgress((int)(1), SummaryText);
                });                backgroundWorker.RunWorkerAsync();
            }            
        }
调用方法：
string vFtpUrl = "yiduoi001.gicp.net";
string vUserID = "ecff";
string vPassWord = "ecSffn";
string vPath = "ecDownload";            
Download(vFtpUrl, vPath, vUserID, vPassWord, @"e:\test\qqbb");  

Answer 9

借贵地咨询另外一个问题，关于文件加密的问题，我想利用XML文件作媒介实现数据交换，但是XML文件用记事本很容打开，对文件的安全性不好，请问用生命方法可以对XML文件内容加密？