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lang: ja-jp
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# SignalR .NET クライアントから Hub に接続しようとするとエラーとなる。 2021-09-08

## コンソールのログ

#### サーバ側

※ `net6.0`

dbug: Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionManager[1]
      New connection cfh_HBMbGbqP4rfcANO3yw created.
dbug: Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionDispatcher[10]
      Sending negotiation response.

#### クライアント側

※コンソールアプリケーション `net6.0`

dbug: Microsoft.AspNetCore.SignalR.Client.HubConnection[40]
      Registering handler for client method 'ReceiveMessage'.
dbug: Microsoft.AspNetCore.SignalR.Client.HubConnection[41]
      Starting HubConnection.
dbug: Microsoft.AspNetCore.Http.Connections.Client.HttpConnection[1]
      Starting HttpConnection.
dbug: Microsoft.AspNetCore.Http.Connections.Client.HttpConnection[8]
      Establishing connection with server at 'http://localhost:5000/ServiceHub_V2'.
fail: Microsoft.AspNetCore.Http.Connections.Client.HttpConnection[10]
      Failed to start connection. Error getting negotiation response from 'http://localhost:5000/ServiceHub_V2'.
      System.Threading.Tasks.TaskCanceledException: The operation was canceled.
       ---> System.IO.IOException: Unable to read data from the transport connection: スレッドの終了またはアプリケーションの要求によって、I/O 処理は中止されました。.
       ---> System.Net.Sockets.SocketException (995): スレッドの終了またはアプリケーションの要求によって、I/O 処理は中止されました。
         --- End of inner exception stack trace ---
         at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ThrowException(SocketError error, CancellationToken cancellationToken)
         at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.GetResult(Int16 token)
         at System.Net.Http.HttpConnection.FillAsync(Boolean async)
         at System.Net.Http.HttpConnection.ReadNextResponseHeaderLineAsync(Boolean async, Boolean foldedHeadersAllowed)
         at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
         --- End of inner exception stack trace ---
         at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
         at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
         at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.Connections.Client.Internal.AccessTokenHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.Connections.Client.Internal.LoggingHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
         at System.Net.Http.HttpClient.SendAsyncCore(HttpRequestMessage request, HttpCompletionOption completionOption, Boolean async, Boolean emitTelemetryStartStop, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.NegotiateAsync(Uri url, HttpClient httpClient, ILogger logger, CancellationToken cancellationToken)

## 単純に私のバグでした

単純に `await` `Task` の記述漏れにより、`connection.StartAsync()` が非同期実行されてました。。。

###### tags: `SignalR` `Hub` `await` `Task`