Understanding Bluetooth Connectivity in iOS Apps

As a developer, integrating Bluetooth connectivity into your iOS app can be a complex task. In this article, we’ll delve into the world of Bluetooth low energy (BLE) and explore how to establish a peer-to-peer connection between two devices using GameKit.

Introduction to GameKit

GameKit is a framework developed by Apple that enables developers to create games and other apps with rich, location-based features. One of its key components is the GameKit Framework’s Peer-to-Peer feature, which allows for direct communication between devices without the need for a central server.

The GameKit Framework provides several APIs for managing peer connections, including:

• GKSession: Represents a session that connects two peers.
• GKPeer: Represents a peer device in a connection.
• GKPeerConnection: Represents a connection between two peers.

Establishing a Peer Connection

To establish a peer connection, we need to create instances of GKSession and GKPeer. Here’s an example code snippet that demonstrates how to create these objects:

// Create a new session
GKSession *session = [[GKSession alloc] initWithName:@"My Session" peerID:nil];

// Get the peer ID for our device
NSString *peerID = [session peerID];

// Create a new peer object
GKPear *peer = [[GKPear alloc] initWithPeerID:peerID];

Sending and Receiving Data

Once we have established a peer connection, we can send and receive data between the two peers using GKSession’s dataSentForAllPeers: method. Here’s an example code snippet that demonstrates how to send data:

- (void) sendData:(NSData *)data {
    [session sendData:data toPeers:[NSOrderedSet setWithObject:peer] withMode:GKTalkerToAllPeers];
}

We can also use receiveData: method in our delegate method receiveData:fromPeer:inSession:context:.

- (void) receiveData:(NSData *)data fromPeer:(NSString *)peer inSession:(GKSession *)session context:(void *)context {
    NSString *str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Chat Message: @" message:str delegate:self cancelButtonTitle:@"REPLY" otherButtonTitles:nil];
    [alert show];
}

Displaying the Peer’s Name in the AlertView

The problem you mentioned is that when displaying the peer’s name in UIAlertView, it seems to be returning a string of 9 or 10 numbers followed by the message. This can be fixed using [session displayNameForPeer:peer]. Here’s how:

NSString *displayName = [session displayNameForPeer:peer];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Chat Message: @" message:[NSString stringWithFormat:@"%@ says: %@", displayName, str] delegate:self cancelButtonTitle:@"REPLY" otherButtonTitles:nil];

Using [session displayNameForPeer:peer]

The displayNameForPeer: method returns the “display name” of a peer. This can be any string that is used to identify the device. When you call this method on your peer object, it should return a display name like "John's iPhone".

This display name is then displayed in UIAlertView when sending a message between peers.

Example Use Case

Here’s an example use case where we’re trying to create a simple peer-to-peer chat app:

// Create a new session
GKSession *session = [[GKSession alloc] initWithName:@"My Chat App" peerID:nil];

// Get the peer ID for our device
NSString *peerID = [session peerID];

// Create a new peer object
GKPear *peer = [[GKPear alloc] initWithPeerID:peerID];

// Set up our delegate method
session.delegate = self;

// Create a new UIAlertView
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Chat Message:" message:nil delegate:self cancelButtonTitle:@"REPLY" otherButtonTitles:nil];

// Send data to the peer

- (void) receiveData:(NSData *)data fromPeer:(NSString *)peer inSession:(GKSession *)session context:(void *)context {
    NSString *str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Chat Message: @" message:str delegate:self cancelButtonTitle:@"REPLY" otherButtonTitles:nil];
    [alertView show];
}

- (void) sendButtonPressed:(id)sender {
    NSString *message = @"Hello World!";
    NSData *data = [message dataUsingEncoding:NSUTF8StringEncoding];
    [session sendData:data toPeers:[NSOrderedSet setWithObject:peer] withMode:GKTalkerToAllPeers];
}

This example creates a new session, gets the peer ID for our device, and sets up a delegate method to handle received data. It then sends a message to the peer when the send button is pressed.

Conclusion

In this article, we’ve explored how to use GameKit’s Peer-to-Peer feature to establish a direct connection between two devices without the need for a central server. We covered topics such as creating sessions and peers, sending and receiving data, and displaying the peer’s name in UIAlertView.

By following these steps and using the provided code snippets, you should be able to create your own simple peer-to-peer chat app that connects multiple devices.

Troubleshooting

If you’re having trouble establishing a peer connection or sending/receiving data, there are several things to check:

• Make sure that both devices have Bluetooth enabled and that the devices are in range of each other.
• Ensure that your devices are running the latest version of iOS.
• Check for any firewall or antivirus software issues that may be blocking your connections.

If you’re still having trouble, try debugging your app to see where the issue is occurring.

Last modified on 2025-02-07