从Azure函数调用Lokalise有时是SocketException:不知道这样的主机

Question

在使用SocketException: No such host is known调用https://api.lokalise.com/api2/projects/{id}/keys时，我们在Azure函数中断断续续地看到日志中的HttpClient。

问题是无法知道问题是来自HttpClient (Microsoft.NETCore.App.Ref\3.1.0\ref\netcoreapp3.1\System.Net.Http.dll)还是来自主机api.lokalise.com。每隔几天，我们就会看到这个问题。

这是一堆东西，

Microsoft.Azure.WebJobs.Host.FunctionInvocationException:
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+<ExecuteWithLoggingAsync>d__26.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:367)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+<TryExecuteAsync>d__18.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:108)
Inner exception System.Net.Http.HttpRequestException handled at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw:
   at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Threading.Tasks.ValueTask`1.get_Result (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1+ConfiguredValueTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<ConnectAsync>d__52.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Threading.Tasks.ValueTask`1.get_Result (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1+ConfiguredValueTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<CreateHttp11ConnectionAsync>d__53.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Threading.Tasks.ValueTask`1.get_Result (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1+ConfiguredValueTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<GetHttpConnectionAsync>d__45.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Threading.Tasks.ValueTask`1.get_Result (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1+ConfiguredValueTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<SendWithRetryAsync>d__47.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.RedirectHandler+<SendAsync>d__4.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.DiagnosticsHandler+<SendAsync>d__2.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpClient+<FinishSendAsyncBuffered>d__70.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at MyApp.Triggers.LokaliseService+<GetTranslations>d__2.MoveNext (MyApp-Triggers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null: D:\home\site\repository\LokaliseService.cs:23)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at MyApp.Triggers.LokaliseService+<GetTranslationString>d__3.MoveNext (MyApp-Triggers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null: D:\home\site\repository\LokaliseService.cs:35)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at MyApp.Triggers.EmailSender+<Run>d__10.MoveNext (MyApp-Triggers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null: D:\home\site\repository\EmailSender.cs:47)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.VoidTaskMethodInvoker`2+<InvokeAsync>d__2.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\VoidTaskMethodInvoker.cs:20)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionInvoker`2+<InvokeAsync>d__10.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionInvoker.cs:52)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+<InvokeWithTimeoutAsync>d__33.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:596)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+<ExecuteWithWatchersAsync>d__32.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:542)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+<ExecuteWithLoggingAsync>d__26.MoveNext (Microsoft.Azure.WebJobs.Host, Version=3.0.32.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:320)
Inner exception System.Net.Sockets.SocketException handled at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext:
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)

更新2022-04-08:我们在没有代码的情况下再次得到了这个错误，这次是连接到https://profiler.monitor.azure.com:443/api/hostagent/v1/config。看起来问题在于HTTP客户端库，而不是loklise。

System.Net.Http.HttpRequestException:
   at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<ConnectAsync>d__52.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<CreateHttp11ConnectionAsync>d__53.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<GetHttpConnectionAsync>d__45.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.HttpConnectionPool+<SendWithRetryAsync>d__47.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.RedirectHandler+<SendAsync>d__4.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.DiagnosticsHandler+<SendAsync>d__2.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
Inner exception System.Net.Sockets.SocketException handled at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext:
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
   at System.Net.Http.ConnectHelper+<ConnectAsync>d__1.MoveNext (System.Net.Http, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)

Answer 1

它看起来像是DNS问题：

tcpclient更喜欢ip地址，而不是名称。

使用Dns.GetHostEntry删除字符并将其更改为ip。

IPHostEntry hostInfo = Dns.GetHostEntry(hostnamehere);

Dns.GetHostEntry将主机名或IP地址解析为IPHostEntry实例。

或

如果抛出异常，您可以尝试捕获异常并实现重试机制。

参考文献：link1 Link2 Link3