如何在C#应用中解决FTP超时 [英] How to solve FTP timeouts in C# app

问题描述

我正在使用以下C#代码从远程服务提供商处通过FTP发送约40MB的CSV文件.大约有50％的时间，下载挂起并最终超时.在我的应用程序日志中，我得到如下一行:

I'm using the following C# code to FTP a ~40MB CSV file from a remote service provider. Around 50% of the time, the download hangs and eventually times out. In my app log, I get a line like:

> Unable to read data from the transport
> connection: A connection attempt
> failed because the connected party did
> not properly respond after a period of
> time, or established connection failed
> because connected host has failed to
> respond.

当我使用LeechFTP等图形客户端以交互方式下载文件时，下载几乎永远不会挂起，并且大约需要45秒才能完成.我真想知道发生了什么事情.

When I download the file interactively using a graphical client like LeechFTP, the downloads almost never hang, and complete in about 45 seconds. I'm having a hell of a time understanding what's going wrong.

任何人都可以建议我如何使用此代码来深入了解正在发生的事情，或者是下载此文件的更好方法吗?我应该增加缓冲区的大小吗?减多少避免缓冲写入磁盘并尝试将整个文件吞入内存?任何建议表示赞赏！

Can anyone suggest how I can instrument this code to get more insight into what's going on, or a better way to download this file? Should I increase the buffer size? By how much? Avoid the buffered writes to disk and try to swallow the whole file in memory? Any advice appreciated!

...

private void CreateDownloadFile()
    {
        _OutputFile = new FileStream(_SourceFile, FileMode.Create);
    }
public string FTPDownloadFile()
    {
        this.CreateDownloadFile();

        myReq = (FtpWebRequest)FtpWebRequest.Create(new Uri(this.DownloadURI));
        myReq.Method = WebRequestMethods.Ftp.DownloadFile;
        myReq.UseBinary = true;
        myReq.Credentials = new NetworkCredential(_ID, _Password);

        FtpWebResponse myResp = (FtpWebResponse)myReq.GetResponse();
        Stream ftpStream = myResp.GetResponseStream();

        int bufferSize = 2048;
        int readCount;
        byte[] buffer = new byte[bufferSize];
        int bytesRead = 0;
        readCount = ftpStream.Read(buffer, 0, bufferSize);

        while (readCount > 0)
        {
            _OutputFile.Write( buffer, 0, readCount );
            readCount = ftpStream.Read( buffer, 0, bufferSize );

            Console.Write( '.' );    // show progress on the console
            bytesRead += readCount;
        }
        Console.WriteLine();
        logger.logActivity( "    FTP received " + String.Format( "{0:0,0}", bytesRead ) + " bytes" );

        ftpStream.Close();
        _OutputFile.Close();
        myResp.Close();
        return this.GetFTPStatus();
    }

    public string GetFTPStatus()
    {
        return ((FtpWebResponse)myReq.GetResponse()).StatusDescription;
    }

推荐答案

我尝试按照上面的建议使用FTPClient，并且遇到了相同的超时错误，FTPClient使用了FtpWebRequest，因此我必须丢失一些内容，但我看不到重点.

I tried to use FTPClient as suggested above and got the same timeout error, FTPClient uses FtpWebRequest so I must be missing something but I don't see the point.

经过更多研究，我发现-1是无穷大

After some more research I found that -1 is the value for infinity

出于我的目的，可以使用无穷大，所以我解决了这个问题.

For my purpose it is okay to use infinity so I went with that, problem solved.

这是我的代码:

//从FTP站点获取文件.

//gets file from FTP site.

        FtpWebRequest reqFTP;

        string fileName = @"c:\downloadDir\localFileName.txt";
        FileInfo downloadFile = new FileInfo(fileName);
        string uri = "ftp://ftp.myftpsite.com/ftpDir/remoteFileName.txt";


        FileStream outputStream = new FileStream(fileName, FileMode.Append);

        reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(uri));
        reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
        reqFTP.UseBinary = true;
        reqFTP.KeepAlive = false;
        reqFTP.Timeout = -1;
        reqFTP.UsePassive = true;
        reqFTP.Credentials = new NetworkCredential("userName", "passWord");
        FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
        Stream ftpStream = response.GetResponseStream();
        long cl = response.ContentLength;
        int bufferSize = 2048;
        int readCount;
        byte[] buffer = new byte[bufferSize];
        readCount = ftpStream.Read(buffer, 0, bufferSize);
        Console.WriteLine("Connected: Downloading File");
        while (readCount > 0)
        {
            outputStream.Write(buffer, 0, readCount);
            readCount = ftpStream.Read(buffer, 0, bufferSize);
            Console.WriteLine(readCount.ToString());
        }

        ftpStream.Close();
        outputStream.Close();
        response.Close();
        Console.WriteLine("Downloading Complete");

这篇关于如何在C#应用中解决FTP超时的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！