public static class AsyncExtensions

{

    public static async Task<T> WithCancellation<T>( this Task<T> task, CancellationToken cancellationToken )

    {

        var tcs = new TaskCompletionSource<bool>();

        using( cancellationToken.Register( s => ( (TaskCompletionSource<bool>)s ).TrySetResult( true ), tcs ) )

        {

            if( task != await Task.WhenAny( task, tcs.Task ) )

            {

                throw new OperationCanceledException( cancellationToken );

            }

        }

​

        return task.Result;

    }

}

​

​

// ... in your code:

try

{

    var data = await client.ReceiveAsync().WithCancellation(cts.Token);

    await client.SendAsync(data.Buffer, data.Buffer.Length, toep).WithCancellation(cts.Token);

}

catch(OperationCanceledException)

{

    client.Close();

}