/// <summary>
/// Send a message to the resource being observed that we want to cancel
/// the observation.
/// </summary>
public void ProactiveCancel()
{
Request cancel = Request.NewGet();
// copy options, but set Observe to cancel
cancel.SetOptions(Request.GetOptions());
cancel.MarkObserveCancel();
// use same Token
cancel.Token = Request.Token;
cancel.Destination = Request.Destination;
// dispatch final response to the same message observers
cancel.CopyEventHandler(Request);
cancel.Send(_endpoint);
// cancel old ongoing request
Request.IsCancelled = true;
Canceled = true;
}
