c#之HttpWebRequest之出现 "Underlying connection was closed"错误

我与这个问题斗争了 2 天，我真的受够了。我发现没有任何效果。

检查这个简单的示例代码:

HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create(updateInfoFileUrl); 
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; //768 for TLS 1.1 and 3072 for TLS 1.2 
ServicePointManager.ServerCertificateValidationCallback = delegate 
{ 
    return true; 
}; 
fileReq.KeepAlive = false; 
 
WebProxy proxy = new WebProxy(); 
proxy.BypassProxyOnLocal = false; 
proxy.UseDefaultCredentials = true; 
proxy.Credentials = CredentialCache.DefaultCredentials; 
fileReq.Proxy = proxy; 
 
HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse(); 
Stream stream = fileResp.GetResponseStream(); 

我尝试了 SecurityProtocols 的不同组合。只使用一个，使用所有这些......没有任何效果。我尝试了 HttpWebRequest、HttpClient 甚至 XmlDocument.Load。什么都不管用。我每次都遇到错误。

它有什么问题？

这是我想阅读的文档: https://www.example.com/info.xml

浏览器显示它。甚至 PostMan 也会显示它。

请您参考如下方法:

做了一些调试。这不是您的代码的问题，但服务器需要用户代理设置。 作品:

HttpWebRequest fileReq = (HttpWebRequest)WebRequest.Create(@"https://www.example.com/info.xml"); 
fileReq.UserAgent = "sadsad"; 
fileReq.Method = "GET"; 
 
HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse(); 
Stream stream = fileResp.GetResponseStream(); 

失败:

HttpWebRequest fileReq = (HttpWebRequest)WebRequest.Create(@"https://www.example.com/info.xml"); 
 
//     fileReq.UserAgent = "sadsad"; 
fileReq.Method = "GET"; 
 
HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse(); 
Stream stream = fileResp.GetResponseStream();