Question

我正在尝试编写一个控制台应用程序

从TcpClient接收已打开的流
从控制台获取输入并将其写入此Stream
收到回复并将其写入控制台。

我尝试使用async / await进行这些操作，但不断获得异常。这是我的代码：

   public void Main()
   {
         while(true)
        {
            WriteAsync(stream);

            ReadAsync(stream);
        }
    }

    private static void ReadAsync(Stream stream)
    {
        using (Stream console = Console.OpenStandardOutput())
         {
           CopyStream(stream, console);
         }


    }

    private static void WriteAsync(Stream stream)
    {
         using (Stream console = Console.OpenStandardInput())
         {
             CopyStream(console, stream);
         }

    }

    private static async void CopyStream(Stream sourceStream, Stream targetStream)
    {
             var buffer = new Byte[256];
             int bytesRead = 0;

             while((bytesRead = await sourceStream.ReadAsync(buffer, 0, buffer.Length)) > 0)
             {
                 await targetStream.WriteAsync(buffer, 0, bytesRead);
             }

    }

这是例外

Unhandled Exception: System.NotSupportedException: Stream does not support reading.
   at System.IO.__Error.ReadNotSupported()
   at System.IO.Stream.BeginReadInternal(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state, Boolean serializeAsynchronously, Boolean apm)
   at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at TestBackend.Program.<CopyStream>d__3.MoveNext() in /home/slavskaya/avl_demonstrator/AVL_SCU/Tests/System/Backend/TestBackend/Program.cs:line 108
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.QueueUserWorkItemCallbackDefaultContext.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()System.NotSupportedException: Stream does not support reading.
   at System.IO.__Error.ReadNotSupported()
   at System.IO.Stream.BeginReadInternal(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state, Boolean serializeAsynchronously, Boolean apm)
   at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at TestBackend.Program.<CopyStream>d__3.MoveNext() in /home/slavskaya/avl_demonstrator/AVL_SCU/Tests/System/Backend/TestBackend/Program.cs:line 108
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.QueueUserWorkItemCallbackDefaultContext.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()System.NotSupportedException: Stream does not support reading.
   at System.IO.__Error.ReadNotSupported()
   at System.IO.Stream.BeginReadInternal(Byte[] buffer, Int32 offset, Int32 count, AsyncCallback callback, Object state, Boolean serializeAsynchronously, Boolean apm)
   at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
   at System.IO.Stream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at TestBackend.Program.<CopyStream>d__3.MoveNext() in /home/slavskaya/avl_demonstrator/AVL_SCU/Tests/System/Backend/TestBackend/Program.cs:line 108
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.QueueUserWorkItemCallbackDefaultContext.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
Aborted

我怀疑我刚刚锁定了流，或者在那里使用异步方法存在其他问题。

所以我尝试创建不同的线程，但它们根本不工作

Task.Run(() =>{
          while(true)
    {
       WriteAsync(stream);
    }
        });
  Task.Run(() =>{
          while(true)
    {
         ReadAsync(stream);
    }
        });

我对异步和多线程都没什么经验，所以你可以指出我，这里的问题在哪里？

Answer 1

你不是等待每个操作，所以它们会重叠太多;你可能想要：

public async Task SomeAsyncMethod()
{
     while(true)
    {
        await WriteAsync(stream);

        await ReadAsync(stream);
    }
}

private static async Task ReadAsync(Stream stream)
{
    using (Stream console = Console.OpenStandardOutput())
     {
       await CopyStream(stream, console);
     }


}

private static async Task WriteAsync(Stream stream)
{
     using (Stream console = Console.OpenStandardInput())
     {
         await CopyStream(console, stream);
     }
}

然而，从非同步Main中调用它是令人烦恼的;只有Wait()

才是个好主意

C＃从控制台应用程序读取/写入流异步

1 个答案: