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iPhone Bluetooth Programming

Learn how to communicate with a server using TCP/IP and also how to build a simple chat application.


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ne of the neat features available in iPhone OS 3.0 is the GameKit framework. The GameKit framework contains APIs to allow communications over a Bluetooth network. Using these APIs, you can create peer-to-peer games and applications with ease. Unlike other mobile platforms, using Bluetooth as a communication channel in iPhone is way easier than expected. Hence, in this article, I will show you how to build a simple application that allows two iPhone or iPod Touch devices to communicate with each other.

Author's Note: To test the concepts covered in this article, you would need two iPhones (3G or 3GS), or iPod Touches (second generation or later) running iPhone OS 3.0 or later.



Creating the Project

Using Xcode, create a new View-based Application project and name it as Bluetooth.

All the various APIs for accessing the Bluetooth is located in the GameKit framework. Hence, you need to add this framework to your project. Add a new Framework to the project by right-clicking on the Frameworks group in Xcode and selecting Add, Existing Frameworks. Select GameKit.framework (see Figure 1).

Figure 1. GameKit: Add the GameKit framework to the project in Xcode.

In the BluetoothViewController.h file, declare the following object, outlets, and actions:

#import #import @interface BluetoothViewController : UIViewController { GKSession *currentSession; IBOutlet UITextField *txtMessage; IBOutlet UIButton *connect; IBOutlet UIButton *disconnect; } @property (nonatomic, retain) GKSession *currentSession; @property (nonatomic, retain) UITextField *txtMessage; @property (nonatomic, retain) UIButton *connect; @property (nonatomic, retain) UIButton *disconnect; -(IBAction) btnSend:(id) sender; -(IBAction) btnConnect:(id) sender; -(IBAction) btnDisconnect:(id) sender; @end

The GKSession object is used to represent a session between two connected Bluetooth devices. You will make use of it to send and receive data between the two devices.

In the BluetoothViewController.m file, add in the following statements in bold:

#import "BluetoothViewController.h" #import @implementation BluetoothViewController @synthesize currentSession; @synthesize txtMessage; @synthesize connect; @synthesize disconnect;

Double-click on BluetoothViewController.xib to edit it in Interface Builder. Add the following views to the View window (see also Figure 2):

  • Text Field

  • Round Rect Button

Figure 2. Nice view: Populate the View window with the various views.

Perform the following actions:

  • Control-click on the File’s Owner item and drag and drop it over the Text Field view. Select txtMessage.

  • Control-click on the File’s Owner item and drag and drop it over the Connect button. Select connect.

  • Control-click on the File’s Owner item and drag and drop it over the Disconnect button. Select disconnect.

  • Control-click on the Send button and drag and drop it over the File’s Owner item. Select btnSend:.

  • Control-click on the Connect button and drag and drop it over the File’s Owner item. Select btnConnect:.

  • Control-click on the Disconnect button and drag and drop it over the File’s Owner item. Select btnDisconnect:.

Right-click on the File’s Owner item to verify that all the connections are made correctly (see Figure 3).

Figure 3. Check it: Verify the connections made for the various outlets and actions.

Back in Xcode, in the BluetoothViewController.m file, add in the following statements in bold:

- (void)viewDidLoad { [connect setHidden:NO]; [disconnect setHidden:YES]; [super viewDidLoad]; } - (void)dealloc { [txtMessage release]; [currentSession release]; [super dealloc]; }

Searching for Peer Devices

Now that all the plumbings for the project have been done, you can now focus on the APIs for accessing other Bluetooth devices.

In the BluetoothViewController.h file, declare a GKPeerPickerController object:

#import "BluetoothViewController.h" #import @implementation BluetoothViewController @synthesize currentSession; @synthesize txtMessage; @synthesize connect; @synthesize disconnect; GKPeerPickerController *picker;

The GKPeerPickerController class provides a standard UI to let your application discover and connect to another Bluetooth device. This is the easiest way to connect to another Bluetooth device.

To discover and connect to another Bluetooth device, implement the btnConnect: method as follows:

-(IBAction) btnConnect:(id) sender { picker = [[GKPeerPickerController alloc] init]; picker.delegate = self; picker.connectionTypesMask = GKPeerPickerConnectionTypeNearby; [connect setHidden:YES]; [disconnect setHidden:NO]; [picker show]; }



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