使用 FluentFTP 从 FTP 同时下载多个文件

Question

我正在使用 FluentFTP 从 FTP 进行连接、下载等操作
https://github.com/robinrodricks/FluentFTP/wiki

我想同时从 List 下载文件。一个个下载没问题。

这就是我的代码的样子：

下载功能：

public async Task<bool> DownloadFileAsync(string RemoteUrl, string AppName, Progress<FtpProgress> progress = null)
    {
        return await Task.Run(async() =>
        {

            using (FileStream read = new FileStream("settings.xml", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                if (ftpClient.IsConnected)
                {
                    if (File.Exists("settings.xml"))
                    {
                        Information info = (Information)xs.Deserialize(read);
                    
                        if (Directory.Exists(info.Downloads))
                        {
                            bool DownloadFinished = await ftpClient.DownloadFileAsync(info.Downloads + "\\" + AppName, RemoteUrl, FtpLocalExists.Overwrite, FtpVerify.Retry, progress);
                            if (DownloadFinished == true)
                            {
                                loger.LogWrite("File " + RemoteUrl + " downloaded succesfully.");
                                //read.Dispose();
                                return true;
                            }
                            else
                            {
                                loger.LogWrite("File" + RemoteUrl + " download failed.");
                                //read.Dispose();
                                return false;
                            }
                        }
                        else
                        {
                            loger.LogWrite("Could not locate folder " + info.Downloads + " downloading terminated.");
                            return false;
                        }
                    }
                    else
                    {
                        MessageBox.Show("settings.xml file is missing.");
                        loger.LogWrite("settings.xml file is missing.");
                        read.Dispose();
                        return false;
                    }
                }
                else
                {
                    loger.LogWrite("FTP Client is not connected could not download: " + RemoteUrl);
                    read.Dispose();
                    return false;
                }
            }
        });

    }

我如何填写列表：

Arta_Variables.ArtaSoftware.Add(new Software() { RemoteUrl = "Ultra_Script/Basic_SW/Adobe_Reader.exe", SoftwareName = "Adobe_Reader.exe", FileExistsOnRemoteUrl = null, Downloaded = null });

这是一个一个下载它们的方法：

if(Arta_Variables.DAAOChecked == false)
{
    if (CheckFinished == true)
    {
        using (FileStream read = new FileStream("settings.xml", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
        {

            XmlSerializer xs = new XmlSerializer(typeof(Information));
            Information info = (Information)xs.Deserialize(read);

            AddBlackLine("");
            AddBlackLine("Downloading all available files.");
            AddBlackLine("");

            foreach (Software software1 in ArtaChosenSW)
            {

                string item = software1.SoftwareName;
                int index = ArtaChosenSW.FindIndex(p => p.SoftwareName == item);

                if (software1.FileExistsOnRemoteUrl == true)
                {
                    AddBlackLine("Downloading " + software1.SoftwareName);

                    Dispatcher.Invoke(() =>
                    {
                        DWGProgressLab.Visibility = Visibility.Visible;
                        DP_ProgressPercentage.Visibility = Visibility.Visible;
                    });

                    Progress<FtpProgress> prog = new Progress<FtpProgress>(x =>
                    {
                        int ConvertedInt = (int)x.Progress;
                        DP_ProgressPercentage.Dispatcher.BeginInvoke((Action)(() => DP_ProgressPercentage.Content = ConvertedInt + "%"));
                    });

                    bool DWFinished = await ftp.DownloadFileAsync(software1.RemoteUrl, software1.SoftwareName, prog);

                    if (DWFinished == true)
                    {
                        AddGreenLine("Download of " + software1.SoftwareName + " succesfull.");
                        ArtaChosenSW[index].Downloaded = true;
                        ArtaChosenSW[index].LocalUrl = info.Downloads;

                        Dispatcher.Invoke(() =>
                        {
                            DWGProgressLab.Visibility = Visibility.Hidden;
                            DP_ProgressPercentage.Visibility = Visibility.Hidden;
                        });

                    }
                    else
                    {
                        AddRedLine("Download of " + software1.SoftwareName + " failed");
                        ArtaChosenSW[index].FileExistsOnRemoteUrl = false;
                    }
                }
                else
                {
                    ArtaChosenSW[index].FileExistsOnRemoteUrl = true;
                    AddBlackLine("File " + software1.SoftwareName + " did not found on ftp. Could not download.");
                    loger.LogWrite("File " + software1.SoftwareName + " did not found on ftp. Could not download.");
                }
            }
        }
    }
}

我尝试同时下载：

foreach(Software software in ArtaChosenSW)
{
    var tasks = ArtaChosenSW.Select(c => Task.Factory.StartNew(() => ftp.DownloadFileAsync(c.RemoteUrl, c.SoftwareName))).ToArray();
    Task.WaitAll(tasks);
}

可悲的是，它在本地 url 中创建了 0kb 的空白文件，但没有进行下载。

我在异步编程方面没有太多经验，所以我会很高兴得到所有答案或一些更好的方法。

Answer 1

您的所有传输似乎都在使用一个FtpClient 实例。

FtpClient 代表一个到 FTP 服务器的连接。 FTP 协议不允许通过一个连接进行多个并行传输。您必须为每次并行传输打开一个新连接。

有关实现示例，请参阅Download multiple files concurrently from FTP using FluentFTP with a maximum value。

Answer 2

从您发布的答案中获取您的代码，这应该可以处理多个下载，而无需任何线程池或 Task 包装器开销。

public async Task DownloadMultipleFilesConcurrentFromFTP(int NumberOfConnections, string AppName, string RemoteUrl)
{
    var downloadTasks = new List<Task>();
    for (int i = 0; i < NumberOfConnections; i++){
        downloadTasks.Add(DownloadFile(AppName, RemoteUrl));
    }
    await Task.WhenAll(downloadTasks);
}
 
public async Task DownloadFile(string AppName, string RemoteUrl)
{
    var ftp = new FtpClient(FTPHost, networkCredential);
    ftp.ConnectTimeout = ConnectTimeout;
    ftp.SocketPollInterval = SocketPollInterval;
    ftp.ReadTimeout = ReadTimeout;
    ftp.DataConnectionConnectTimeout = DataConnectionConnectTimeout;
    ftp.DataConnectionReadTimeout = DataConnectionReadTimeout;
    await ftp.ConnectAsync();
    if (ftp.IsConnected)
    {
        using (FileStream read = new FileStream("settings.xml", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
        {
            if (ftp.IsConnected == true)
            {
                if (File.Exists("settings.xml"))
                {
                    Information info = (Information)xs.Deserialize(read);
                    if (Directory.Exists(info.Downloads))
                    {
                        await ftp.DownloadFileAsync(info.Downloads + "\\" + AppName, RemoteUrl, FtpLocalExists.Overwrite, FtpVerify.Retry);
                    }
                }
            }
        }
    }
}

它为每次下载创建一个Task，然后在任务列表上调用Task.WhenAll，等待所有文件完成后再返回。

我没有修改您的任何文件处理代码，但您也应该考虑使用async 版本的调用，因为使用阻塞调用访问文件系统可能会导致响应问题。

Answer 3

根据@Martin Prikryl 的回答，我为并发下载创建了新功能：

完美运行：

public async Task DownloadMultipleFilesConcurrentFromFTP(int NumberOfConnections, string AppName, string RemoteUrl)
{
    await Task.Run(async() =>
    {
        NetworkCredential networkCredential = new NetworkCredential(FTPUsername, FTPPassword);
        List<FtpClient> ftpClients = new List<FtpClient>();

        for (int i = 0; i < NumberOfConnections; i++)
        {
            ftpClients.Add(new FtpClient(FTPHost, networkCredential));
            foreach(FtpClient ftp in ftpClients)
            {
                ftp.ConnectTimeout = ConnectTimeout;
                ftp.SocketPollInterval = SocketPollInterval;
                ftp.ReadTimeout = ReadTimeout;
                ftp.DataConnectionConnectTimeout = DataConnectionConnectTimeout;
                ftp.DataConnectionReadTimeout = DataConnectionReadTimeout;
                ftp.Connect();
                if (ftp.IsConnected)
                {
                    using (FileStream read = new FileStream("settings.xml", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        if(ftp.IsConnected == true)
                        {
                            if (File.Exists("settings.xml"))
                            {
                                Information info = (Information)xs.Deserialize(read);
                                if (Directory.Exists(info.Downloads))
                                {
                                    await ftp.DownloadFileAsync(info.Downloads + "\\" + AppName, RemoteUrl, FtpLocalExists.Overwrite, FtpVerify.Retry);
                                }
                            }
                        }
                    }
                }
            }
        }
    });
}

现在我只需要弄清楚如何返回所有文件的下载进度。