Sergiy Baydachnyy

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Azure Mobile Services: Creating a simple Notification Hub

with 5 comments

Lately I made a short overview of Notification Hub but the last article was mostly about some benefits of Notification Hub in comparison to “native” solution rather than its features. Today, I am planning to concentrate your attention on a step-by-step guideline, which will show how to use Notification Hub and will provide much more details about its particular features.

The first of all, we should understand that Microsoft has prepared several boxed solutions for common mobile scenarios, which are called Azure Mobile Services. However, Notification Hub service is NOT one of them. This service does not require Mobile Services and we are able to create it using App Services tab.

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However, there will be several opportunities, if we associate Notification Hub and Mobile Services. That is why I propose to start with Mobile Services and if we will create ones, Notification Hub will be created automatically for us.

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This step is very simple. You should select name (url), SQL Database and region. The Backend field helps to select right technology for backend coding and you can select between .NET (C# of course) and JavaScript options. I do not like JavaScript very much but I would recommend the JavaScript language for Notification Hub scenarios because you will not create much code due to limited number of them. Frankly speaking, there is one scenario only and it relates to registration process of new devices. Additionally, it is easy to deploy JavaScript registration script because Azure dashboard has special options as well as JavaScript editor, which should make you deployment process pretty simple. In any case, I am planning to show JavaScript as well as C# in the next article. Therefore, you can use any of those languages.

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If you click OK, you will have your Mobile Service as well as Notification Hub inside in 1-2 minutes. There are several ways to open Hub dashboard but I like the Mobile Services tab because it allows to edit JavaScript registration script as well as to change permissions of registration endpoints. These permissions allow to setup additional security rules for endpoints, which will be used to register new devices. There are the following options:

· Everyone – all devices will be able to pass registration process. It’s OK for many scenarios because the registration activity itself will not allow to receive any notifications in case of wrong certificate (or client secret and package sid in case of Windows 8);

· Anybody with application key – this option allows to pass registration process for devices, which sent an application key in their requests. Pay attention, that this method will not guarantee any type security for apps because, in the most cases, developers store an application key inside their applications and key can be stolen very easy. If you want to add some security features, you should implement authentication mechanism inside your app;

· Only Authenticated Users – users require to authenticate via one of the supported authentication providers like Facebook, Twitter, Google, Microsoft Account and Azure Active Directory;

· Only Script and Admins – only script with master key as well as admin (via Management Portal) will be able to use the service;

Pay special attention that you will not see registration endpoints section, if you select .NET as a backend technology. If you use C#, you will be able to set permissions WebApiConfig.cs file.

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We just discussed the security options and we mentioned application key and master key. They can be found on Mobile Service dashboard and you can easily regenerate these keys in case of leaks.

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Of course, you should be aware of Media Services security options just in case of using Media Services client libraries but you can work with Notification Hub to avoid Media Services and it does not depend on whether your Notification Hub is integrated with Media Services in you subscription.

If you want work with Notification Hub directly, you may forget about application and master keys but you will need to apply the policies of Notification Hub. In order to understand these policies, let’s go to Notification Hub dashboard (Configure tab). You can find there several access policies and you are able to modify them or create new ones. We should use these policies in order to connect Notification Hub directly. Additionally, there are two keys for each policy, which should be used for connection strings. You can find all the connection strings on the Dashboard page of Notification Hub and you can select one of them based on existing permissions. Of course, if you need a connection string for client devices, which will listen to notifications only, you can use DefaultListenAccessSignature connection string. If you create backend service, which will send Notifications, you can use a connection string with Send permission etc.

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Ok, I think that we can create a simple application, which will be able to receive our notifications. In order to do it I selected Windows Phone application (Silverlight) because this type of applications doesn’t require Store registration but it requires to turn on Enable unauthenticated push notifications checkbox on the Configure tab. It will allow to send up to 500 messages without certificate and this number is enough for testing.

Let’s open Visual Studio and create Windows Phone (Silverlight) application. It will use old type of notification services unlike Windows Runtime applications but it will not require a certificate as mentioned above.

We will try to communicate with Notification Hub directly as well as via Mobile Service. I will start with the direct method. In order to do this you should use NuGet tool to add WindowsAzure.Messaging.Managed assembly, which will help you to send data to our hub because I don’t want to create JSon code as well as work with WebRequest and WebResponse classes.

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Right now, we are ready to add some code. Open App.xaml.cs file and change Application_Launching method in the following way:

private async void Application_Launching(object sender, LaunchingEventArgs e)

{

    var channel = HttpNotificationChannel.Find("MyPushChannel2");

    if (channel == null)

    {

        channel = new HttpNotificationChannel("MyPushChannel2");

        channel.Open();

        channel.BindToShellToast();

    }

 

    channel.ChannelUriUpdated +=

       new EventHandler<NotificationChannelUriEventArgs>(async (o, args) =>

    {

        var hub = new NotificationHub("test-ms-sbaydachhub",

            "<connection string>");

        await hub.RegisterNativeAsync(args.ChannelUri.ToString());

 

    });

}

This code will allow to receive Notification Channel from the MPNS and update the channel in our Notification Hub. That’s all. You can run the application on your phone and try to send a message. In order to send a message you can use the Debug tab on the Azure Management Portal.

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If you want to use Mobile Services in order to register your device for notifications, you need to add Azure Mobile Service package to your project and change Application_Launching in the following way:

private async void Application_Launching(object sender, LaunchingEventArgs e)

{

    var channel = HttpNotificationChannel.Find("MyPushChannel2");

    if (channel == null)

    {

        channel = new HttpNotificationChannel("MyPushChannel2");

        channel.Open();

        channel.BindToShellToast();

    }

 

    channel.ChannelUriUpdated +=

       new EventHandler<NotificationChannelUriEventArgs>(async (o, args) =>

        {

 

            MobileServiceClient MobileService = new MobileServiceClient(

                "https://test-ms-sbaydach.azure-mobile.net/&quot;

 

            );

            await MobileService.GetPush().

               RegisterNativeAsync(channel.ChannelUri.ToString());

        });

}

Pay your attention that this code doesn’t use connection strings from Notification Hub but it will not work if you don’t set Everyone permission to the registration pipeline (or put an application key as a second parameter of MobileServiceClient constructor).

I think we can finish for today. In the next article I am planning to create a Windows Runtime application as well as an application for sending push notifications.

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Written by Sergiy Baydachnyy

09/21/2014 at 10:21 PM

5 Responses

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