Question

我写了一段从网址下载文件的简单代码。此代码在Windows 7中运行良好，以良好的速度下载文件并维护显示下载进度的进度条。但是，当我从Windows XP SP2运行相同的代码时，它会产生.NET IOException ，对我来说没有意义，为什么它不起作用。它启动相同，正确完成第一次读取，然后在第二次尝试从流中读取时抛出以下异常：

 System.IO.IOException: Unable to read data from the transport connection: An operation on a
 socket could not be performed because the system lacked sufficient buffer space or because a
 queue was full. ---> 

 System.Net.Sockets.SocketException: An operation on a socket could not be  
 performed because the system lacked sufficient buffer space or because a queue was full
 at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)

 at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
 --- End of inner exception stack trace ---
 at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
 at ServicePackChk.SrvPackChk.DownLoadServicePack(Boolean bWindowsXP)
 at ServicePackChk.SrvPackChk.CheckServicePackStatus()
 at ServicePackChk.Form1.Form1_Load(Object sender, EventArgs e)
 at System.Windows.Forms.Form.OnLoad(EventArgs e)

代码：

        Uri uri;

        if (bWindowsXP)
            uri = new Uri("http://download.microsoft.com/download/d/3/0/d30e32d8-418a-469d-b600-f32ce3edf42d/WindowsXP-KB936929-SP3-x86-ENU.exe");
        else
            uri = null;

        WebRequest req = WebRequest.Create(uri);
        WebResponse resp = req.GetResponse();

        ProgBarForm pform = new ProgBarForm();

        updateEvent += new SrvPackChk.UpdateDownloaded(pform.UpdateProgBar);

        Stream stream = resp.GetResponseStream();
        ArrayList alBytes = new ArrayList();
        int nLen = (int)resp.ContentLength;


        pform.DownLoadSize = nLen;

        pform.Show();

        byte[] byExe = new byte[nLen];

        bool bMoreToDownload = true;

        FileStream fs = new FileStream(System.IO.Path.GetTempPath() + "XPSP3.exe", FileMode.Create);

        MessageBox.Show("Saving File to " + System.IO.Path.GetTempPath() + "XPSP3.exe");

        while (bMoreToDownload)
        {
            Application.DoEvents();

            int nRead = 0;

            nRead = stream.Read(byExe, 0, nLen);

            nDownloaded += nRead;

            updateEvent(nDownloaded);

            if (nDownloaded == nLen)
            {
                bMoreToDownload = false;
            }

            fs.Write(byExe, 0, nRead);
            fs.Flush();

            Application.DoEvents();
        }

        stream.Close();

        fs.Close();

Answer 1

您下载的文件超过300兆字节，您尝试从流中一次读取。

您最好以块方式读取流，例如4MByte块。

下载代码适用于Windows 7但不适用于XP SP2？

1 个答案: