c# - 为什么在 C# 中使用 HttpClient 时出现“响应提前结束”?
问题描述
我在 .Net Core 中的第一个 HTTP 客户端代码。服务器也在我的 PC 上运行,所以我想将它发送到 localhost。
在有人在这里推荐之后,我添加了内部异常的打印,但这还不足以让我理解这个问题。
namespace HTTPClient
{
// The object I want to send
public class Msg
{
public string ID { get; set; }
public string Data { get; set; }
public int RSSIR { get; set; }
public int RSSIT { get; set; }
public int Slot { get; set; }
}
class Program
{
static Msg msg = new Msg
{
ID = "00CC",
Data = "9F4CC",
RSSIR = 123,
RSSIT = 321,
Slot = 1
};
static void Main(string[] args)
{
string url = "http://127.0.0.1:5001";
Console.WriteLine("result = " , callURL(url));
Console.ReadKey();
}
public static bool callURL(string url)
{
ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;
bool Result = false;
HttpClient client = new HttpClient();
client.BaseAddress = new Uri(url);
client.DefaultRequestHeaders.Accept.Clear();
HttpResponseMessage response = null;
try
{
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpContent content = new StringContent(JsonConvert.SerializeObject(msg), Encoding.UTF8, "application/json");
response = client.PostAsync("", content).Result;
}
catch (AggregateException err)
{
foreach (var errInner in err.InnerExceptions)
{ // for printing the inner execption
Console.WriteLine("ERROR");
Console.WriteLine(errInner);
}
}
if (response.IsSuccessStatusCode)
{
Result = true;
}
else
{
Result = false;
}
return Result;
}
}
}
我从 catch 内的循环中收到的错误是:
System.Net.Http.HttpRequestException: An error occurred while sending the request.
---> System.IO.IOException: The response ended prematurely.
at System.Net.Http.HttpConnection.FillAsync()
at System.Net.Http.HttpConnection.ReadNextResponseHeaderLineAsync(Boolean foldedHeadersAllowed)
at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithNtConnectionAuthAsync(HttpConnection connection, HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
我怎样才能弄清楚为什么我不能向服务器发送消息?消息的内容是否会中断连接生成?
我用另一个客户端检查了服务器并且它正在工作,所以问题必须在我的代码中。
编辑:服务器正在使用 https,所以我也将我的 URL 更改为 https,这是我收到的错误:
System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.
at System.Net.Security.SslStream.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception)
at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.PartialFrameCallback(AsyncProtocolRequest asyncRequest)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Security.SslStream.ThrowIfExceptional()
at System.Net.Security.SslStream.InternalEndProcessAuthentication(LazyAsyncResult lazyResult)
at System.Net.Security.SslStream.EndProcessAuthentication(IAsyncResult result)
at System.Net.Security.SslStream.EndAuthenticateAsClient(IAsyncResult asyncResult)
at System.Net.Security.SslStream.<>c.<AuthenticateAsClientAsync>b__65_1(IAsyncResult iar)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
我是否需要添加一些 SSL 命令才能建立安全连接?
Edit2:在 callURL() 中添加命令后的新错误
---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.
at System.Net.Security.SslStream.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception)
at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.PartialFrameCallback(AsyncProtocolRequest asyncRequest)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Security.SslStream.ThrowIfExceptional()
at System.Net.Security.SslStream.InternalEndProcessAuthentication(LazyAsyncResult lazyResult)
at System.Net.Security.SslStream.EndProcessAuthentication(IAsyncResult result)
at System.Net.Security.SslStream.EndAuthenticateAsClient(IAsyncResult asyncResult)
at System.Net.Security.SslStream.<>c.<AuthenticateAsClientAsync>b__65_1(IAsyncResult iar)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
解决方案
System.IO.IOException: The response ended prematurely
表示您向其发出 HTTP 请求的服务器在未发回完整响应的情况下关闭了连接。
它与您的客户端代码无关,因为它看起来可以正确编译和发送内容。
是的,您应该使用await client.PostAsync
,但这与您的问题完全无关。
仔细检查http://127.0.0.1:5001
100% 正确 - 也许它在https://
或不在 port 上5001
。
如果它是使用 HTTPS 的端点,您可能会得到System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.
,因为看起来您正在调用本地端点。
.NET 默认进行 SSL 证书验证,如果您尝试调用没有/无效 SSL 证书的 HTTPS 端点,则会引发异常。您可能没有在您的机器上正确设置 localhost 证书。
ServicePointManager.ServerCertificateValidationCallback
现在,您可以通过设置为始终返回true
来绕过检查HttpClientHandler.DangerousAcceptAnyServerCertificateValidator
初始化您的HttpClient
如下所示:
public static bool callURL(string url)
{
bool Result = false;
var httpClientHandler = new HttpClientHandler();
#if DEBUG
httpClientHandler.ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator;
#endif
HttpClient client = new HttpClient(httpClientHandler);
...
}
但是,请注意,如果在本地开发环境以外的任何地方使用,允许所有 SSL 证书存在安全风险。
阅读:世界上最危险的代码:斯坦福大学在非浏览器软件中验证 SSL 证书
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