[英]Exception when downloading file using webclient (c#)
I'm using ac# code to download files from a website. 我正在使用ac#代码从网站下载文件。 I'm using the webclient class: 我正在使用webclient类:
using (var client = new WebClient())
{
client.DownloadFile(
@"http://www.cftc.gov/files/dea/history/com_disagg_txt_2018.zip",
@"destination"
);
}
The code worked fine for several weeks. 该代码可以正常工作几个星期。 But it ceased to work about a week ago. 但是大约一周前它停止工作了。 Whenever I run the code it throws an exception saying: 每当我运行代码时,它都会引发异常:
An existing connection was closed by the remote host. 远程主机已关闭现有连接。 (Error code 10054) (错误代码10054)
I was thinking that perhaps the website started to allow only download via browser so I added: 我在想,也许网站开始只允许通过浏览器下载,所以我补充道:
client.Headers["User-Agent"] ="Mozilla/5.0 (Windows NT 6.3; rv:36.0)
Gecko/20100101 Firefox/36.0";
However, it did not resolve the issue. 但是,它没有解决问题。
Does anybody know a solution? 有人知道解决方案吗?
This failure is quite common. 这种失败很常见。
That Site has implemented TLS 1.2
protocol. 该站点已实施TLS 1.2
协议。
The Protocol is switched to
Https:
even if you specifiedHttp:
in your URI. 即使您在URI中指定了Http:
,协议也会切换为Https:
You simply have to enable it, since .Net ServicePointManager
(still) defaults to Ssl3/Tls 1.0
. 您只需启用它即可,因为.Net ServicePointManager
(仍然)默认为Ssl3/Tls 1.0
。
Test it with this code: 使用以下代码对其进行测试:
string Url ="http://www.cftc.gov/files/dea/history/com_disagg_txt_2018.zip";
Uri URI = new Uri(Url, UriKind.Absolute);
WebClient_DownLoad(URI, FileName);
public void WebClient_DownLoad(Uri URI, string FileName)
{
using (WebClient webclient = new WebClient())
{
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
webclient.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.BypassCache);
webclient.Headers.Add(HttpRequestHeader.UserAgent, "Mozilla/5.0 (Windows NT 10; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0");
webclient.Headers.Add(HttpRequestHeader.Accept, "ext/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
webclient.Headers.Add(HttpRequestHeader.AcceptLanguage, "en-US,en;q=0.8");
webclient.Headers.Add(HttpRequestHeader.AcceptEncoding, "gzip, deflate;q=0.8");
webclient.Headers.Add(HttpRequestHeader.CacheControl, "no-cache");
webclient.Headers.Add(HttpRequestHeader.KeepAlive, "keep-alive");
webclient.UseDefaultCredentials = true;
webclient.DownloadFileCompleted += new AsyncCompletedEventHandler(WebClient_DownloadComplete);
webclient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(WebClient_DownloadProgress);
webclient.DownloadFileAsync(URI, FileName);
};
}
private void WebClient_DownloadProgress(object sender, DownloadProgressChangedEventArgs e)
{
string Result = string.Format("Received: {0} Total: {1} Percentage: {2}",
e.BytesReceived, e.TotalBytesToReceive, e.ProgressPercentage);
//Update the UI
Console.WriteLine(Result);
}
private static void WebClient_DownloadComplete(object sender, AsyncCompletedEventArgs e)
{
if (!e.Cancelled)
{
if (e.Error != null)
// Update the UI: transfer completed.
Console.WriteLine("Error: " + e.Error.Message);
}else{
// Update the UI: transfer Cancelled.
Console.WriteLine("Cancelled");
}
}
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