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Question

这个想法很简单,我正在创建一个服务,用户可以在其中放置托管在另一个网站上的文件的直接链接,我的程序将打开一个流到该远程服务器并开始以字节为单位读取文件,然后返回每个readed字节给用户.

到目前为止,我设法让这工作,这是我的代码

    public void Index()
    {
        //Create a stream for the file
        Stream stream = null;

        //This controls how many bytes to read at a time and send to the client
        int bytesToRead = 10000; //10000

        // Buffer to read bytes in chunk size specified above
        byte[] buffer = new Byte[bytesToRead];

        // The number of bytes read
        try
        {
            //Create a WebRequest to get the file
            HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create("http://SOME-OTHER-SERVER.com/File.rar");


            //Create a response for this request
            HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse();


            if (fileReq.ContentLength > 0)
                fileResp.ContentLength = fileReq.ContentLength;

            //Get the Stream returned from the response
            stream = fileResp.GetResponseStream();

            // prepare the response to the client. resp is the client Response
            var resp = HttpContext.Response;

            //Indicate the type of data being sent
            resp.ContentType = "application/octet-stream";

            //Name the file 
            resp.AddHeader("Content-Disposition", "attachment; filename=\"" + "fle.rar" + "\"");
            resp.AddHeader("Content-Length", (fileResp.ContentLength).ToString());

            int length;
            do
            {
                // Verify that the client is connected.
                if (resp.IsClientConnected)
                {
                    // Read data into the buffer.
                    length = stream.Read(buffer, 0, bytesToRead);

                    // and write it out to the response's output stream
                    resp.OutputStream.Write(buffer, 0, length);

                    // Flush the data
                    resp.Flush();

                    //Clear the buffer
                    buffer = new Byte[bytesToRead];
                }
                else
                {
                    // cancel the download if client has disconnected
                    length = -1;
                }
            } while (length > 0); //Repeat until no data is read
        }
        finally
        {
            if (stream != null)
            {
                //Close the input stream
                stream.Close();
            }
        }
    }

当我进入我的页面时它下载完美,但问题是如果我停止下载它将不会再次恢复.

我搜索了这个问题,并发现有一个标题"Accept-Ranges"必须在连接中定义才能支持简历.

所以我添加了标题,但没有奏效.

Answer 1

处理范围请求比这复杂一点.一般来说,你需要处理Range,并If-Range在请求头和适当的服务206个部分内容与反应Content-Range,Date以及ETag或Content-Location头.

文章在ASP.NET MVC范围请求- RangeFileResult详细描述了如何创建ASP.NET MVC ActionResult与范围请求支持.

在您的情况下,您还必须检查另一方(您使用的那一方fileReq)是否支持范围请求.如果是,则可以只请求所需的部分(并且最好在本地缓存它),但如果不是,则需要获取整个文件并寻找适当的位置(在这种情况下,您肯定希望拥有本地缓存​​方案).