CancellationTokenSource - Stream - problem

Question

I want an event when the disconnect button is pressed or the server closes.

I can't get into the cancellation. Why? What's wrong?

The problem is

I can't get there. Disconnect and abort.

Why not? What's wrong?

         try      
          {   
             // MyCancellationTokenSource = new CancellationTokenSource();
             // while (true) //stream.DataAvailable) //(true)
             while (MyCancellationTokenSource.IsCancellationRequested) //stream.DataAvailable) //(true)
             {
                 int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, MyCancellationTokenSource.Token);

 public class MyTcpClient
 {
     private TcpClient _client;


     CancellationTokenSource MyCancellationTokenSource = new CancellationTokenSource();

     public event EventHandler<string> MessageReceived;

     /// <summary>
     /// Connect to the TCP server
     /// </summary>
     /// <param name="ipAddress"></param>
     /// <param name="port"></param>
     public void Connect(string ipAddress, int port)
     {
         _client = new TcpClient();
         _client.Connect(ipAddress, port);

         // Start a separate task to receive data
         _ = ReceiveDataAsync();

         // _ = Task.Run(async () => await ReceiveDataAsync());
     }

     /// <summary>
     /// Send message to the connected server
     /// </summary>
     /// <param name="message"></param>
     public void SendMessage(string message)
     {
         NetworkStream stream = _client.GetStream();
         byte[] buffer = Encoding.ASCII.GetBytes(message);
         stream.Write(buffer, 0, buffer.Length);
     }

     /// <summary>
     /// Handle incoming data from the server
     /// </summary>
     private async Task ReceiveDataAsync()
     {
         NetworkStream stream = _client.GetStream();
         byte[] buffer = new byte[1024];
         StringBuilder messageBuilder = new StringBuilder();

         try
         {
             //MyCancellationTokenSource = new CancellationTokenSource();
             while (true) //stream.DataAvailable) //(true)
             {
                 int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, MyCancellationTokenSource.Token);

                 if (bytesRead == 0)
                 {
                     break; // Server or client disconnected
                 }

                 string data = Encoding.ASCII.GetString(buffer, 0, bytesRead);
                 messageBuilder.Append(data);

                 if (data.Length > 0)
                 {
                     string receivedMessage = messageBuilder.ToString();
                     OnMessageReceived(receivedMessage);
                     messageBuilder.Clear();
                 }
             }

             _client.Close();
         }
         catch (OperationCanceledException)
         {
             Console.WriteLine("Cancel XXXX");
         }
     }

     public void Disconnect()
     {
         MyCancellationTokenSource.Cancel();

         _client?.Close();
     }

     protected virtual void OnMessageReceived(string message)
     {
         MessageReceived?.Invoke(this, message);
     }
 }

Answer 1

you are using the default stream implementation, which does nothing when the token is canceled (thus no error thown). to get the read to exit, you close the socket as your Disconnect code does. just add the error throw.

var token = MyCancellationTokenSource.Token;
int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, token);
token.ThrowIfCancellationRequested();
    

Answer 2

Thanks for reaching out! 

1.  Make sure the stream is still open when you cancel. If you close the stream before cancellation, ReadAsync may exit silently without throwing.
2. Add a Disconnect Event, then call OnDisconnected() in both places:

• After bytesRead == 0
• Inside catch (OperationCanceledException)

     3.Update your loop to handle both cancellation and disconnectionThanks for reaching out!