Question

我正在尝试使用FtpWebRequest下载文件。

private void DownloadFile(string userName, string password, string ftpSourceFilePath, string localDestinationFilePath)
{
    int bytesRead = 0;
    byte[] buffer = new byte[1024];

    FtpWebRequest request = CreateFtpWebRequest(ftpSourceFilePath, userName, password, true);
    request.Method = WebRequestMethods.Ftp.DownloadFile;

    Stream reader = request.GetResponse().GetResponseStream();
    BinaryWriter writer = new BinaryWriter(File.Open(localDestinationFilePath, FileMode.CreateNew));

    while (true)
    {
        bytesRead = reader.Read(buffer, 0, buffer.Length);

        if (bytesRead == 0)
            break;

        writer.Write(buffer, 0, bytesRead);
    }        
}

它使用我创建的CreateFtpWebRequest方法：

private FtpWebRequest CreateFtpWebRequest(string ftpDirectoryPath, string userName, string password, bool keepAlive = false)
{
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(new Uri(ftpDirectoryPath));

    //Set proxy to null. Under current configuration if this option is not set then the proxy that is used will get an html response from the web content gateway (firewall monitoring system)
    request.Proxy = null;

    request.UsePassive = true;
    request.UseBinary = true;
    request.KeepAlive = keepAlive;

    request.Credentials = new NetworkCredential(userName, password);

    return request;
}

下载它。但信息总是被破坏。有谁知道发生了什么事？

Answer 1

刚想通了：

    private void DownloadFile(string userName, string password, string ftpSourceFilePath, string localDestinationFilePath)
    {
        int bytesRead = 0;
        byte[] buffer = new byte[2048];

        FtpWebRequest request = CreateFtpWebRequest(ftpSourceFilePath, userName, password, true);
        request.Method = WebRequestMethods.Ftp.DownloadFile;

        Stream reader = request.GetResponse().GetResponseStream();
        FileStream fileStream = new FileStream(localDestinationFilePath, FileMode.Create);

        while (true)
        {
            bytesRead = reader.Read(buffer, 0, buffer.Length);

            if (bytesRead == 0)
                break;

            fileStream.Write(buffer, 0, bytesRead);
        }
        fileStream.Close();       
    }

不得不改为使用FileStream。

Answer 2

使用.NET框架从FTP服务器下载文件的最简单方法是使用WebClient.DownloadFile method：

WebClient client = new WebClient();
client.Credentials = new NetworkCredential("username", "password");
client.DownloadFile(
    "ftp://ftp.example.com/remote/path/file.zip", @"C:\local\path\file.zip");

如果您只需要更大的控件，请使用FtpWebRequest class WebClient类不提供（如TLS / SSL加密，进度监控等）。一种简单的方法是使用Stream.CopyTo方法将FTP响应流复制到FileStream：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Ftp.DownloadFile;

using (Stream ftpStream = request.GetResponse().GetResponseStream())
using (Stream fileStream = File.Create(@"C:\local\path\file.zip"))
{
    ftpStream.CopyTo(fileStream);
}

仅限，如果您需要监控下载进度，则必须自行复制内容：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Ftp.DownloadFile;

using (Stream ftpStream = request.GetResponse().GetResponseStream())
using (Stream fileStream = File.Create(@"C:\local\path\file.zip"))
{
    byte[] buffer = new byte[10240];
    int read;
    while ((read = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
    {
        fileStream.Write(buffer, 0, read);
        Console.WriteLine("Downloaded {0} bytes", fileStream.Position);
    }
}

对于GUI进度（WinForms ProgressBar），请参阅：
FtpWebRequest FTP download with ProgressBar

如果要从远程文件夹下载所有文件，请参阅
C# Download all files and subdirectories through FTP

使用FtpWebRequest下载文件

2 个答案: