Question

我的代码在通过FTP下载大文件后30分钟后遇到超时异常。服务器在Windows上运行FileZilla。我们配置了SSL证书，其中启用了选项Enable FTP over SSL/TLS support (FTPS)和Allow explicit FTP over TLS。我可以访问服务器和FileZilla配置，但看不到任何可能导致此行为的内容。下面是在Windows 2012 Server Machine上运行在.NET 4.6.2上的源代码。它可以从FTP服务器下载文件，但如果文件下载时间超过30分钟，则会在30分钟后超时（如下所列）。

作为测试，我使用FileZilla Client从同一客户端PC运行，同时从同一服务器端点下载多个大文件，以便每个文件的下载花费30多分钟才能完成。在这种情况下没有发生错误。

我搜索了StackOverflow以及Google，但没有任何有希望的事情发生了。如果有人有关于在哪里寻找（服务器端或客户端）的一些提示，我将非常感激。

申请代码

public class FtpFileDownloader
{
    // log4net
    private static readonly ILog Logger = LogManager.GetLogger(typeof(FtpFileDownloader));

    public void DownloadFile()
    {
        // setting the SecurityProtocol did not change the outcome, both were tried. Originally it was not set at all.
        // ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;


        ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true;

        const int timeout = 7200000;
        const string file = "some-existing-file";
        try
        {
            var request = (FtpWebRequest) WebRequest.Create("uri-path-to-file");
            request.KeepAlive = false;
            request.Timeout = -1;
            request.ReadWriteTimeout = timeout;

            request.Credentials = new NetworkCredential("userName", "password");
            request.UsePassive = true;
            request.EnableSsl = true;
            request.Method = WebRequestMethods.Ftp.DownloadFile;

            Logger.Debug($"Downloading '{file}'");
            using (var response = (FtpWebResponse) request.GetResponse())
            using (var sourceStream = response.GetResponseStream())
            using (var targetStream = new FileStream("some-target-on-disk", FileMode.Create, FileAccess.Write))
            {
                try
                {
                    sourceStream.CopyTo(targetStream);
                    targetStream.Flush();
                    Logger.Debug($"Finished download '{file}'");
                }
                catch (Exception exInner)
                {
                    Logger.Error($"Error occurred trying to download file '{file}'.", exInner);
                }
            }
        }
        catch (Exception ex)
        {
            Logger.Error($"Error occurred trying to dispose streams when downloading file '{file}'.", ex);
        }
    }
}

应用程序日志

ERROR FtpFileDownloader - Error occurred trying to download file 'some-existing-file'.
System.IO.IOException: Received an unexpected EOF or 0 bytes from the transport stream.
   at System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count)
   at System.Net.Security._SslStream.StartFrameBody(Int32 readBytes, Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security._SslStream.StartFrameHeader(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security._SslStream.StartReading(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security._SslStream.ProcessRead(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.TlsStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.FtpDataStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.IO.Stream.InternalCopyTo(Stream destination, Int32 bufferSize)
   at System.IO.Stream.CopyTo(Stream destination)
   at FtpFileDownloader.DownloadFile

ERROR FtpFileDownloader - Error occurred trying to dispose streams when downloading file 'some-existing-file'.
System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive.
   at System.Net.FtpWebRequest.SyncRequestCallback(Object obj)
   at System.Net.FtpWebRequest.RequestCallback(Object obj)
   at System.Net.CommandStream.Dispose(Boolean disposing)
   at System.IO.Stream.Close()
   at System.IO.Stream.Dispose()
   at System.Net.ConnectionPool.Destroy(PooledStream pooledStream)
   at System.Net.ConnectionPool.PutConnection(PooledStream pooledStream, Object owningObject, Int32 creationTimeout, Boolean canReuse)
   at System.Net.FtpWebRequest.FinishRequestStage(RequestStage stage)
   at System.Net.FtpWebRequest.SyncRequestCallback(Object obj)
   at System.Net.FtpWebRequest.RequestCallback(Object obj)
   at System.Net.CommandStream.Abort(Exception e)
   at System.Net.CommandStream.CheckContinuePipeline()
   at System.Net.FtpWebRequest.DataStreamClosed(CloseExState closeState)
   at System.Net.FtpDataStream.System.Net.ICloseEx.CloseEx(CloseExState closeState)
   at System.Net.FtpDataStream.Dispose(Boolean disposing)
   at System.IO.Stream.Close()
   at System.IO.Stream.Dispose()
   at FtpFileDownloader.DownloadFile

FileZilla - 常规设置

 Listen on these ports: 21
  Max. number of users: 0 (infinite)
     Number of threads: 2
    Connection timeout: 120 (seconds)
   No Transfer timeout: 9000 (seconds)
           Log timeout: 60 (seconds)

FileZilla Server Log

23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> Connected on port 21, sending welcome message...
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> 220 Welcome
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> AUTH TLS
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> 234 Using authentication type TLS
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> TLS connection established
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> USER  my-user-account
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> 331 Password required for my-user-account
23-2-2018 11:40:40 - (not logged in) (194.123.75.2)> PASS **************
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 230 Logged on
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> PBSZ 0
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 200 PBSZ=0
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> PROT P
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 200 Protection level set to P
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> OPTS utf8 on
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 202 UTF8 mode is always enabled. No need to send this command.
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> PWD
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 257 "/" is current directory.
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> TYPE I
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 200 Type set to I
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> PASV
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 227 Entering Passive Mode (IP-ADDRESS,245,222)
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> RETR path-to-file
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> 150 Opening data channel for file download from server of "/path-to-file"
23-2-2018 11:40:40 - my-user-account (194.123.75.2)> TLS connection for data connection established
23-2-2018 12:10:41 - my-user-account (194.123.75.2)> disconnected.

请注意断开连接（最后一行）与其前一行之间有30分钟。如果它已成功完成转移，那么在226 Successfully transferred "/path-to-file"行

之前还会有一行读取disconnected

进度更新：

（2018.02.20）我要求我们的网络团队检查防火墙规则，但他们找不到任何有趣的东西。
（2018.02.22）我发现正在使用的FileZilla Server的版本是0.9.43 beta（发布日期2014-01-02，根据更改日志）。虽然我在更改日志中没有找到任何表明此行为曾经是固定错误的内容，但我将升级到最新版本0.9.60.2（发布日期2017-02-08 ）并且再次执行测试。将在24小时内回复。
（2018.02.23）FileZilla已更新至最新版本。这并没有解决问题，我更新了服务器日志，但它看起来几乎与之前的日志完全相同，但最后一次转移是通过TLS而不是SSL进行的。
（2018.02.23）我在FileZilla支持页面上找到了以下链接Timeouts on large files。我将把它推回给我们托管服务提供商的网络工作人员再看看。
（2018.02.27）原来，公司防火墙（客户端执行的网络）而不是托管防火墙（托管FileZilla的网络）是罪魁祸首。它被配置为在1800秒后丢弃空闲连接。已添加规则以在这两个端点之间覆盖此值。

罪魁祸首/答案

事实证明，公司防火墙（客户端执行的网络）而不是托管防火墙（托管FileZilla的网络）是罪魁祸首。它被配置为在1800秒后丢弃空闲连接。已添加规则以在这两个端点之间覆盖此值。

Answer 1

可能您应该尝试另一种不基于FtpWebRequest构建的FTP协议客户端实现。

相关问题长期存在，他们没有明确的解决方案或答案。所以我会尝试类似FluentFTP的东西，它直接使用Winsock API。 XML文档注释指出DownloadFile()应该很好地处理大文件下载：

/// <summary>
/// Downloads the specified file onto the local file system.
/// High-level API that takes care of various edge cases internally.
/// Supports very large files since it downloads data in chunks.
/// </summary>

有关详细信息，请查看：

Downloading large files(~150MB) from FTP server hangs关于StackOverflow的讨论
FtpWebRequest is Broken Matt Mitchell的文章
Winsock API页面
Elmue的Partial FTP Downloader文章中的源代码部分

Answer 2

是的，我不认为这是一个错误＆＃34;在你的代码中;它只是控制连接在30分钟后消失，即使传输连接没有超时。也许它甚至不需要改变你的KeepAlive和Timeout值，只需尝试每20分钟左右重复一次虚拟下载：这样你就可以重置控制连接计时器。

顺便说一下，我已经读过30分钟是FileZilla Server的标准超时，它基于6个keep-alive配置为每300秒发送一次（这给你30分钟的体验）。如果您可以尝试使用另一台FTP / FTPS服务器，您可能会发现一个不同的空闲超时，并且不会反对该30分钟的限制（但是不同的限制）。

所以，我个人会投资制作async以下的代码，因此执行流程会在封闭的using之后继续，您可以输入一个循环，每20分钟重复一次您的请求（和它的控制连接）进行虚拟下载。当然，FileZilla Client不需要虚拟下载，因为它在较低级别运行，并且可能发送TCP命令以保持控制连接处于活动状态。

using (var response = (FtpWebResponse) request.GetResponse())
        using (var sourceStream = response.GetResponseStream())
        using (var targetStream = new FileStream("some-target-on-disk", FileMode.Create, FileAccess.Write))
        {
            try
            {
                sourceStream.CopyTo(targetStream);
                targetStream.Flush();
                Logger.Debug($"Finished download '{file}'");
            }
            catch (Exception exInner)
            {
                Logger.Error($"Error occurred trying to download file '{file}'.", exInner);
            }
        }

Answer 3

有类似的issue reported in FluentFTP here和stefanolazzarato posted a work-around：

int progress = -1;
try
{
   FtpClient client = new FtpClient("HOST");
   client.Credentials = new NetworkCredential("USER", "PASSWORD");
   client.Connect();

   client.UploadFile("LOCALPATH/FILENAME", "REMOTEPATH/FILENAME",
       FtpExists.Overwrite,
       false,
       FtpVerify.None,
       new Progress<FtpProgress>(p => progress = Convert.ToInt32(p.Progress))
       );
}
catch (Exception ex)
{
   if (progress == 100 && ex is FluentFTP.FtpException && ex.InnerException != null && ex.InnerException is TimeoutException)
   {
       // Upload complete
       // LOG Info exception
   }
   else
   {
       // LOG Fatal exception
       throw;
   }
}

FtpWebRequest 30分钟超时

申请代码

应用程序日志

FileZilla - 常规设置

FileZilla Server Log

罪魁祸首/答案

3 个答案: