Subscribing to Notifications

For the final function, you will set up a subscription to be notified when a new item is added to the inbox. There are three types of subscriptions:

• The first, called a pull notification, happens when the client makes periodic calls to check for updates since the last call. This works by subscribing to the notification service and then polling that service for changes. A watermark is set each time the service is polled. Any changes that occurred since the last watermark are returned. This can easily be done in application code, but it does require polling the service. Notifications are not sent back to the subscription object automatically. Either some type of user event must be used to trigger the application to check the service or some sort of timer must be used.