Cancel C# 4.5 TcpClient ReadAsync by timeout

Question

What would the proper way to cancel TcpClient ReadAsync operation by timeout and catch this timeout event in .NET 4.5?

TcpClient.ReadTimeout seems to be applied to

Answer 1

Passing a CancellationToken to ReadAsync() doesn't add much value because it checks the status of the token only before it starts reading:

// If cancellation was requested, bail early with an already completed task.
// Otherwise, return a task that represents the Begin/End methods.
return cancellationToken.IsCancellationRequested
            ? Task.FromCanceled(cancellationToken)
            : BeginEndReadAsync(buffer, offset, count);

You can quite easily add a timout mechanism yourself by waiting for either the ReadAsync() or the timout task to complete like this:

byte[] buffer = new byte[128];
TimeSpan timeout = TimeSpan.FromSeconds(30);

var readTask = stream.ReadAsync(buffer, 0, buffer.Length);
var timeoutTask = Task.Delay(timeout);
await Task.WhenAny(readTask, timeoutTask);
if (!readTask.IsCompleted)
{
    throw new TimeoutException($"Connection timed out after {timeout}");
}