SMS Interception in Windows Mobile 5.0

Write an application that runs on your smartphone to query any phone that can send and receive SMSes for information and also act on that information. Our sample here queries for unread messages on the phone

Wednesday, March 08, 2006

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Windows Mobile 5.0 lets developers write applications for PocketPC and Smartphone for a variety of scenarios. One such good feature is SMS Interception which lets an SMS is received be intercepted by your application which can then perform some action on the message. In this article, we are going to discuss this feature and build a real life application around the following scenario. As a scenario, imagine that you have forgotten your PocketPC or Smartphone at home. It's possible that people call you up (only to know that no one is answering as the phone is unattended) or SMS you. Since the phone is at home, you do not know the number of missed calls you got (and from whom) or messages you received. Our sample will let you query your phone for the number of unread SMS you got, from any cellphone which is capable of sending SMS.

Introducing SMS interception
The SMS interception functionality for Windows Mobile 5.0 is based on the 'Microsoft.WindowsMobile.PocketOutlook. MessageInterception' namespace that is implemented in the 'Microsoft.WindowsMobile.PocketOutlook' assembly. To set up an application, create an object of the type 'MessageInterceptor' (declared at the class level so that it lives for the lifetime of the application) and set up an event handler for its 'MessageReceived' event.

interceptor = new MessageInterceptor(

            InterceptionAction.Notify);

interceptor.MessageReceived += new MessageInterceptorEvent Handler(interceptor_MessageReceived);

The Activate button when clicked activates or deactivates SMS interception by the smartphone our application is installed on

This initialization of message interception is done typically in the Form's Load event as it is required just once. The constructor, as you can see, takes an argument that defines what kind of action the system will take on the intercepted message. After initializing the interception, the handler is implemented. Interception can be either as Notify in which case the message is checked and moved to the device's inbox; or NotifyAndDelete which would process and delete the message from the device.

 void interceptor_MessageReceived(object sender,

            MessageInterceptorEventArgs e) {    

            SmsMessage sms = (SmsMessage)e.Message;

}

The 'MessageInterceptorEventArgs' object contains a Message property, which can be casted to 'SmsMessage' type, to extract the SMS message contents.That sets up our message interception.

Building QueryDevice
'QueryDevice' is our Windows Mobile 5.0 application that can be queried for a number of unread SMSes from any other phone capable of sending them. We start off by creating a new Windows Mobile 5.0 Pocket PC device application. Windows Mobile 5.0 applications can be designed using VS .NET 2005. Once this IDE has been installed, you can install the Windows Mobile 5.0 SDKs from this month's PCQLive! CD. Once you install one of them, you will see the PocketPC and/or Smartphone templates in VS .NET.

When creating a PocketPC device application, we add a reference to Microsoft.WindowsMobile and Microsoft.WindowsMobile.PocketOutlook assemblies and imports the following three namespaces in our code: Microsoft.WindowsMobile, Microsoft. WindowsMobile.PocketOutlook, and Microsoft.WindowsMobile. PocketOutlook.MessageInterception. The second and third namespaces are both implemented in the 'Microsoft.WindowsMobile. PocketOutlook' assembly. Next, we switch to the design view and drop a button control on the form and set its Text property to Activate as shown below. Add a Click event handler and write the below code to activate message interception or deactivate it.

if (btnActivate.Text.IndexOf("Activate") != -1)

{

   interceptor = new MessageInterceptor(InterceptionAction.

Notify);

   interceptor.MessageReceived += new MessageInterceptorEventHandler(interceptor_MessageReceived);

             btnActivate.Text = "Deactivate";

}

if (btnActivate.Text.IndexOf("Deactivate") != -1)

{

   interceptor.Dispose();

   interceptor = null;

   btnActivate.Text = "Activate";

}

Now, we are all set to activate and deactivate message interception on demand. All we need to do is to implement the event handler to invoke when messages are intercepted to check what the user wants to know (unread SMS count, unread e-mail count). To do this, we need to define commands for our application. We will define three commands: getunreadsms, getunreademail and getunreadmms to retrieve the number of unread SMS, email and MMS messages from the device.

To perform one of the three, simply send an SMS to that phone with the command name (eg: getunreadsms) and the application on the phone would intercept this SMS, find the number and reply with the result. To do all this, our application needs to use the the SystemState class that's defined in the Microsoft.Windows Mobile.Status namespace. Status assembly and import the namespace, Microsoft.WindowsMobile.Status. We are all set now to implement our event handler to process the intercepted SMS and process it.

Inside message interception handler
The message interception handler takes an argument of type MessageInterceptorEventArgs with a Message property that returns a reference to the SmsMessage object (intercepted SMS).

Below is the code for the message interception handler that exemplifies this and also how to process the commands we defined:

void interceptor_MessageReceived(object sender,

MessageInterceptorEventArgs e)

{

   SmsMessage sms = (SmsMessage)e.Message;

   string strFrom = sms.From.Address;

   string strMessageText = sms.Body.Trim().ToLower();

   bool bGotCommand = false;

   string strReplyMessage = "";

   switch (strMessageText)

   {

       case "getunreadsms":

          strReplyMessage = "Unread SMS: "+SystemState.MessagingSmsUnread;

          bGotCommand = true;

          break;

       case "getunreademail":

          strReplyMessage = "Unread Email: "+SystemState.MessagingTotalEmailUnread;

          bGotCommand = true;

          break;

      case "getunreadmms":

         strReplyMessage = "Unread MMS: "+SystemState.MessagingMmsUnread;

         bGotCommand = true;

         break;

   }

   if (bGotCommand == true)

   {

      SmsMessage replySMS = new SmsMessage();

      replySMS.To.Add(new Recipient(strFrom));

      replySMS.Body = strReplyMessage;

      replySMS.Send();

   }

}

Upon getting the reference to the intercepted SMS, we extract its message body and also the address of the sender. Next, we set a flag to indicate if we found any command in the message body to process. We use a switch-case to check for the presence of any of the defined commands, and if found, we use the SystemState class to get the

information from the OS.Once out of the switch-case, we check if we found a command, and if so, we proceed to create a reply SMS to sender of the command with the data we got. And that's all there is to querying your device for information, even if you forgot it at home! Once activated, it will respond to you no matter where you are! It took us just 35 lines of code to implement it (excluding the commands and braces, but does include the namespace import statements specific to Windows Mobile 5.0)!  

Kumar Gaurav Khanna