Windows Phone 8 : Using Push Notifications (part 2) - Setting Up the Server for Push Notifications

For example, we can have an ASP.NET web project that hosts a WCF service that accepts the channel URI from the phone. In this example, I’ve set up a simple database to hold the channel URIs as well as a WCF service that can accept the channel URIs. The WCF service interface looks simple enough:

[ServiceContract]
public interface IMyPhoneService
{
  [OperationContract]
  void RegisterPhoneApp(string channelUrl);
}

The expectation is that the phone will call a service method with the channel URI when it receives it so that the server has a list of people to notify. It would be common to include additional information, but for this example let’s keep it simple. The implementation of the service would look like this:

public void RegisterPhoneApp(string channelUrl)
{
  // Add to list of URIs to notify
  using (var ctx = new PhoneEntities())
  {
    if (ctx.Phones.Where(p => p.PhoneUrl == channelUrl).Count() == 0)
    {
      var phone = Phone.CreatePhone(0, channelUrl, DateTime.Now);
      ctx.Phones.AddObject(phone);
      ctx.SaveChanges();
    }
  }
}

In this case the code just uses the Entity Framework to store the channel URI in the database for use later. This means the phone code has to change to actually use this web service. To do this, you can just create a small helper method that calls the service:

void SendChannelUriToService(string uri)
{
  var client = new MyPhoneServiceClient();

  // Handle the completed event
  client.RegisterPhoneAppCompleted += (s, e) =>
    {
      if (e.Error != null)
      {
        // Log Error (User Can't Fix this error)
      }
    };

  // Send the channel URI to the server
  client.RegisterPhoneAppAsync(uri);
}

Now that you have the helper method, you can call this when you have the channel URI:

public void CreateChannel()
{
  try
  {
    if (_myChannel == null)
    {
      // Attempt to get the channel
      _myChannel = HttpNotificationChannel.Find(CHANNELNAME);

      // Can't Find the Channel, so create it
      if (_myChannel == null)
      {
        _myChannel = new HttpNotificationChannel(CHANNELNAME);

        // Add Event Handlers
        _myChannel.ChannelUriUpdated += myChannel_ChannelUriUpdated;

        // Open the channel since it's a new channel
        _myChannel.Open();
      }
      else
      {
        // Add Event Handlers
        _myChannel.ChannelUriUpdated += myChannel_ChannelUriUpdated;
      }

      // If the channel uri is valid now, then send it to the server
      // Otherwise it'll be registered when the URI is updated
      if (_myChannel.ChannelUri != null)
      {
        // Use the ChannelUri to tell your server about the phone
        SendChannelUriToService(_myChannel.ChannelUri.ToString());
      }
    }

    return;
  }
  catch (Exception)
  {
    MessageBox.Show("Failed to create Push Notification Channel");
  }
}

...

void myChannel_ChannelUriUpdated(object sender,
                                 NotificationChannelUriEventArgs e)
{
  // Use the ChannelUri to tell your server about the phone
  SendChannelUriToService(e.ChannelUri.ToString());
}

With the channel URI in hand, you are ready to push notification messages to the phone!

Authenticating Push Notifications

The MPNS can use a custom certificate you send to Microsoft during the submission process for authenticating your phone. Push notifications are specifically from your own server(s).