C# HttpClient 现有连接被远程主机强行关闭

Question

我正在使用他们的 hosted page integration 与 Alternative Payments 进行集成。他们的 C# SDK 目前没有此集成可用，但如您所见，它非常简单，我做了一个小 class 来发送 post 请求并获得 JSON 响应。

我测试了 json object 我在 PostMan 和 cURL 上发送并且都工作，还有身份验证 header，所以我认为它们不是问题。这是我的 class:

的构造函数

public AlternativePaymentsCli(string apiSecretKey)
{
    this._apiSecretKey = apiSecretKey;

    _httpClient = new HttpClient();
    _httpClient.DefaultRequestHeaders.Accept
        .Add(new MediaTypeWithQualityHeaderValue("application/json"));

    var authInfo = _apiSecretKey;
    authInfo = Convert.ToBase64String(System.Text.ASCIIEncoding.ASCII.GetBytes(string.Format("{0}:", _apiSecretKey)));

    // The two line below because I saw in an answer on Whosebug.
    _httpClient.DefaultRequestHeaders.Add("Connection", "Keep-Alive"); 
    _httpClient.DefaultRequestHeaders.Add("Keep-Alive", "3600");

    _httpClient.DefaultRequestHeaders.UserAgent.ParseAdd("Anything.com custom client v1.0");
    _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", authInfo);

}

以及我post获取数据的方法：

public string CreateHostedPageTransaction(HostedPageRequest req) 
{
    var settings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore };

    // I send this same json content on PostMan and it works. The json is not the problem
    var content = new StringContent(JsonConvert.SerializeObject(req, settings), Encoding.UTF8, "application/json");
    var response = _httpClient.PostAsync(this._baseUrl + "/transactions/hosted", content).Result;
    var responseText = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();

    if (response.IsSuccessStatusCode)
        return responseText;

    return "";
}

然后我在 PostAsync 行收到此错误：An existing connection was forcibly closed by the remote host。这是错误详情：

[SocketException (0x2746): An existing connection was forcibly closed by the remote host]
   System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult) +8192811
   System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult) +47

[IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.]
   System.Net.TlsStream.EndWrite(IAsyncResult asyncResult) +294
   System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar) +149

[WebException: The underlying connection was closed: An unexpected error occurred on a send.]
   System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context) +324
   System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar) +137

[HttpRequestException: An error occurred while sending the request.]

我正在使用 C# 4.5，Asp.Net MVC。我一直在阅读相同错误的答案，到目前为止，其中 none 解决了我的问题。我在这段代码中遗漏了什么？

感谢您的帮助

Answer 1

我在您的代码示例中没有看到您在哪里设置 _baseUrl 的值，但我假设这是在某处完成的。我还假设因为这与付款有关，所以 URL 是 HTTPS。如果远程主机已禁用 TLS 1.0 而您的连接以 TLS 1.0 的形式进入，则可能会导致该行为。我知道 C# 4.6 默认启用 TLS 1.0/1.1/1.2 支持，但我认为 C# 4.6 仍然默认仅 SSL3/TLS 1.0，即使支持 TLS 1.1 和 1.2。如果这是问题的原因，您可以使用以下代码手动将 TLS 1.1 和 1.2 添加到已启用的值。

System.Net.ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

Answer 2

如果您使用的是 .Net 4.0，则未定义 SecurityProtocolType.Tls11 和 SecurityProtocolType.Tls2，因此您可以使用下面的硬编码值。

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

Answer 3

可以在不更改代码的情况下解决问题，如中描述的类似问题：

将 Web 项目重新定位到 .Net 4.6+，然后更新 web.config 如下：

<system.web>
  <compilation targetFramework="4.6" /> 
  <httpRuntime targetFramework="4.6" /> 
</system.web>

Answer 4

这对我有用，第一行确保协议 ssl3 和 TLS1.2，第二行忽略任何潜在的证书错误（忽略并继续 - 如过期的证书。）：

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12;
ServicePointManager.ServerCertificateValidationCallback +=  (sender, certificate, chain, sslPolicyErrors) => true;

Answer 5

对我来说，这个错误是由于忘记配置代理服务器造成的。使用以下代码构造 HttpClient 为我的 .NET 4.7.2 应用程序解决了它：

var httpClientHandler = new HttpClientHandler { Proxy = WebRequest.GetSystemWebProxy() };
var httpClient = new HttpClient(httpClientHandler);

希望这对某人有所帮助。

C# HttpClient 现有连接被远程主机强行关闭

C# HttpClient An existing connection was forcibly closed by the remote host

c#

asp.net

json

dotnet-httpclient