Windows 服务上的 C# HttpWebRequest：更改请求中的任何 属性 不会产生效果

Question

我写了一个 Windows WCF 服务（运行 作为本地系统）从网络服务器获取请求，其中一个数据验证步骤是，将它们再次发送到网络服务器 (https )，它正在做这项工作。

现在我正在尝试使用 "HttpWebRequest" class 发送请求。

以下执行我的请求：（参数：字符串 a_Body 包含字符串化 Json ）

// Accept all certificates
ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) =>
{
    return true;
};

// Encode given Json coded Data to Bytearray
byte[] formData = Encoding.UTF8.GetBytes( a_Body );

HttpWebRequest req = WebRequest.Create(new Uri( ApiVerifyUrl )) as HttpWebRequest;
req.KeepAlive = false;
req.Method = "POST";
req.Accept = "application/json";
req.ContentType = "application/json";

// Test Header, to see, if it would be set!
req.Headers.Add("X-Test", "Test123");

req.ContentLength = formData.Length;

// fiddler connection
req.Proxy = new WebProxy("[ip]", [port]);

using (Stream post = req.GetRequestStream()) // <- throws error ( see log below )
{
    post.Write( formData, 0, formData.Length );
    post.Close();
}

HttpWebResponse resp = (HttpWebResponse)req.GetResponse();

我也捕获了一个异常，whis 被抛出：

using (Stream post = req.GetRequestStream())

异常详情：

[21.11.2018 08:36:21] Emergency:  
An exception "WebException" occurred:  
 - Message:   
   Die zugrunde liegende Verbindung wurde geschlossen: Unerwarteter Fehler beim Senden..  
   (= The Connection was closed: unexpected error)  
 - Source:   
   System  
 - Target:   
   System.IO.Stream GetRequestStream(System.Net.TransportContext ByRef)  
 - Stack Trace:   
   bei System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)  
   bei System.Net.HttpWebRequest.GetRequestStream()  
   bei Intrasearch.Service.HttpServer.ValidateRequestByApi(String a_Body)   
 - InnerException: "IOException":  
    - Message:   
      Von der Übertragungsverbindung können keine Daten gelesen werden: Eine   vorhandene Verbindung wurde vom Remotehost geschlossen.
      (= Data cant be read from the Connection: Remotehost closed the connection)
    - Source:   
      System  
    - Target:   
      Int32 Read(Byte[], Int32, Int32)    
    - Stack Trace:   
      bei System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)  
      bei System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count)  
      bei System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer,   AsyncProtocolRequest asyncRequest)  
      bei System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)   
      bei System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)  
      bei System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)  
      bei System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)  
      bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)  
      bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)  
      bei System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)  
      bei System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)  
      bei System.Net.ConnectStream.WriteHeaders(Boolean async)   
 - InnerException: "SocketException":
       - Message: 
         Eine vorhandene Verbindung wurde vom Remotehost geschlossen 
         (= An Connection was closed by the remotehost) 
       - Source:   
         System  
       - Target:   
         Int32 Read(Byte[], Int32, Int32)  
       - Stack Trace:  
         bei System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) 

现在我要问： 为什么我的Attributes没有设置好，导致请求无法正常建立连接？ 相同的代码在具有相同 Web 服务器的控制台应用程序中运行。 我现在正在搜索几天。

Answer 1

我使用了不支持 Tls 1.2 的旧版本 .Net Framework (4.0)。 我们的服务器限制了任何没有 Tls 1.2 的连接，所以发生了这个错误。

我只是将 .Net 版本更改为 4.5 并添加了：

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

现在可以使用了！