CancellationTokenSource - Stream - problem

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);
     }
 }