The document discusses using Multipeer Connectivity to synchronize data between iOS devices without an internet connection. It provides an overview of Multipeer Connectivity and its classes for discovery, advertising, and sharing data in sessions between nearby peers. Examples are given for sharing images, streaming data, and building a shared whiteboard app using gestures and drawings sent over Multipeer Connectivity sessions. Further examples are mentioned for simple synchronization of data between devices and using third party libraries to enable syncing of Core Data apps.

1. Synchronizing
without internet
Codemotion 2014, Madrid

2. Who am I?
Jorge Maroto
(@patoroco)
http://maroto.me
· iOS Developer
@ticketeaeng
· Playing with iOS since
2010
· Fanboy

3. Synchronize

7. ¿Internet?

8. LAN (wired / wi-fi)

9. What about iOS?

10. Changelog
· iOS 3: Game Kit
· iOS 4: Game Center
· iOS 5: Core Bluetooth
· iOS 6: Core Bluetooth advertising
· iOS 7: Multipeer Connectivity &
iBeacons
· iOS 8: Handoff

11. Changelog
· iOS 3: Game Kit
· iOS 4: Game Center
· iOS 5: Core Bluetooth
· iOS 6: Core Bluetooth advertising
· iOS 7: Multipeer Connectivity &
iBeacons
· iOS 8: Handoff

12. Multipeer
Connectivity

13. Multipeer connectivity
· Appears in iOS7.
· Ability to connect to a mesh of peers.
· Able to connect to peers over WiFi, ad-hoc
wireless, and Bluetooth.
· Doesn't require server infraestructure.
· Peers must be 'nearby'.

16. MultipeerConnectivity.framework
Bonjour | CFNetwork

17. Two phases
· Discovery
· Session

18. Classes
#import <MultipeerConnectivity/MultipeerConnectivity.h>
Session info
Discovery
Advertisement

19. Session info
· MCPeerId
· MCSession

20. MCPeerId
MCPeerID *peerId =
[[MCPeerID alloc] initWithDisplayName:self.deviceName];

21. MCSession
MCSession *session =
[[MCSession alloc] initWithPeer:self.peerId];
session.delegate = self;

22. <MCSessionDelegate>
- (void)session:(MCSession *)session
peer:(MCPeerID *)peerID
didChangeState:(MCSessionState)state
{
switch (state):
{
case MCSessionStateConnected:
...
case MCSessionStateConnecting:
...
case MCSessionStateNotConnected:
...
}
}

23. <MCSessionDelegate>
// DATA
- (void)session:(MCSession *)session
didReceiveData:(NSData *)data
fromPeer:(MCPeerID *)peerID {}
// RESOURCES
- (void)session:(MCSession *)session
didStartReceivingResourceWithName:(NSString *)resourceName
fromPeer:(MCPeerID *)peerID
withProgress:(NSProgress *)progress {}
- (void)session:(MCSession *)session
didFinishReceivingResourceWithName:(NSString *)resourceName
fromPeer:(MCPeerID *)peerID atURL:(NSURL *)localURL
withError:(NSError *)error{}
// STREAMS
- (void)session:(MCSession *)session
didReceiveStream:(NSInputStream *)stream
withName:(NSString *)streamName
fromPeer:(MCPeerID *)peerID{}

24. Discovery · MCBrowserViewController
· MCNearbyServiceBrowser

25. MCBrowserViewController
NSString * const serviceIdentifier = @"codemotion-demo";
MCBrowserViewController *browser =
[[MCBrowserViewController alloc] initWithServiceType:serviceIdentifier
session:self.appdelegate.session];
browser.delegate = self;
[self presentViewController:browser animated:YES completion:nil];

27. <MCBrowserViewControllerDelegate>
- (void)browserViewControllerDidFinish:(MCBrowserViewController *)b {}
- (void)browserViewControllerWasCancelled:(MCBrowserViewController *)b {}

28. Advertisement
· MCAdvertiserAssistant
· MCNearbyServicesAdvertiser

29. MCAdvertiserAssistant
NSString * const serviceIdentifier = @"codemotion-demo";
MCAdvertiserAssistant *advertiser =
[[MCAdvertiserAssistant alloc]
initWithServiceType:self.serviceIdentifier
discoveryInfo:nil session:session];
[advertiser start];

30. Session phase

31. Sending data
· NSData to an array of peers.
· NSURL resource to a peer.
· NSStream to a peer.

32. Send NSData to an array of peers
- (BOOL)sendData:(NSData *)data
toPeers:(NSArray *)peerIDs
withMode:(MCSessionSendDataMode)mode
error:(NSError **)error;
Modes
· MCSessionSendDataReliable
· MCSessionSendDataUnreliable

33. DEMO Hello world in MC

34. Video

36. Send resource to a peer
- (NSProgress *)sendResourceAtURL:(NSURL *)resourceURL
withName:(NSString *)resourceName
toPeer:(MCPeerID *)peerID
withCompletionHandler:(void(^)(NSError *error))completionHandler;

37. Example Share images from photo
library

38. @property (weak, nonatomic) IBOutlet UIImageView *picture;

39. - (IBAction)choosePhoto:(UIButton *)sender
{
UIImagePickerController *picker = [[UIImagePickerController alloc] init];
picker.delegate = self;
picker.allowsEditing = NO;
picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
picker.mediaTypes = @[(NSString *)kUTTypeImage];
[self presentViewController:picker animated:YES completion:nil];
}

40. <UIImagePickerDelegate>
#pragma mark - UIImagePickerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage *selectedImage = info[UIImagePickerControllerOriginalImage];
NSData *jpegImg = UIImageJPEGRepresentation(selectedImage, 0.5);
NSString *tmpPath = [NSTemporaryDirectory() stringByAppendingString:@"pic.jpg"];
self.imageURL = [NSURL fileURLWithPath:tmpPath];
[jpegImg writeToURL:self.imageURL atomically:NO];
self.picture.image = selectedImage;
[picker dismissViewControllerAnimated:YES completion:nil];
}
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
[picker dismissViewControllerAnimated:YES completion:NULL];
}

41. <MCSessionDelegate>
#pragma mark -
- (void)session:(MCSession *)session
didStartReceivingResourceWithName:(NSString *)resourceName
fromPeer:(MCPeerID *)peerID withProgress:(NSProgress *)progress
{
dispatch_async(dispatch_get_main_queue(), ^{
self.picture.image = nil;
self.picture.backgroundColor = [UIColor yellowColor];
});
}
- (void)session:(MCSession *)session
didFinishReceivingResourceWithName:(NSString *)resourceName
fromPeer:(MCPeerID *)peerID atURL:(NSURL *)localURL
withError:(NSError *)error
{
NSData *data = [NSData dataWithContentsOfURL:localURL];
UIImage *image =
[[UIImage alloc] initWithData:data];
dispatch_async(dispatch_get_main_queue(), ^{
self.picture.image = image;
});
}

42. Video Share images from photo
library

44. Streaming - (NSOutputStream *)startStreamWithName:(NSString *)streamName
toPeer:(MCPeerID *)peerID
error:(NSError **)error;

45. NSOutputStream: open
- (void)session:(MCSession *)session
peer:(MCPeerID *)peerID
didChangeState:(MCSessionState)state
{
...
if (state == MCSessionStateConnected)
{
NSError *error;
NSOutputStream *output =
[session startStreamWithName:@"streamName" toPeer:peer error:&error];
if (error) { return; }
[output scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
[output open];
}
...
}

46. NSOutputStream: write
NSData *data = [NSData data];
[self.output write:data.bytes maxLength:data.length];

47. NSInputStream
- (void)session:(MCSession *)session
didReceiveStream:(NSInputStream *)stream
withName:(NSString *)streamName
fromPeer:(MCPeerID *)peerID
{
stream.delegate = self;
[stream scheduleInRunLoop:[NSRunLoop mainRunLoop]
forMode:NSDefaultRunLoopMode];
[stream open];
}

48. <NSStreamDelegate>
- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
switch (eventCode) {
case NSStreamEventOpenCompleted:
...
case NSStreamEventEndEncountered:
...
case NSStreamEventHasBytesAvailable:
{
NSInputStream *inputStream = (NSInputStream *)aStream;
uint8_t buffer[1024];
NSInteger size = [inputStream read:(uint8_t *)buffer maxLength:1024];
NSData *data = [NSData dataWithBytes:buffer length:size];
...
// Manage data received
...
break;
}
default:
break;
}
}

49. Example Shared whiteboard

51. UIPanGestureRecognizer
- (IBAction)panReceived:(UIPanGestureRecognizer *)sender
{
CGPoint point = [sender locationInView:sender.view];
[self.drawable drawPoint:point state:sender.state];
NSData *data =
[NSData drawDataWithGestureState:sender.state
point:[sender locationInView:sender.view]];
[self.output write:data.bytes maxLength:data.length];
}

52. - (void)drawPoint:(CGPoint)point state:(UIGestureRecognizerState)state
{
switch (state) {
case UIGestureRecognizerStateBegan:
{
lastPoint = point;
break;
}
case UIGestureRecognizerStateChanged:
{
CGPoint currentPoint = point;
UIGraphicsBeginImageContext(self.layout.frame.size);
[self.tmpLayout.image drawInRect:CGRectMake(0, 0, self.layout.frame.size.width, self.layout.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 10);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0, 0, 0, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
self.tmpLayout.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tmpLayout setAlpha:1];
UIGraphicsEndImageContext();
lastPoint = currentPoint;
break;
}
case UIGestureRecognizerStateEnded:
{
UIGraphicsBeginImageContext(self.layout.frame.size);
[self.layout.image drawInRect:CGRectMake(0, 0, self.layout.frame.size.width, self.layout.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
[self.tmpLayout.image drawInRect:CGRectMake(0, 0, self.layout.frame.size.width, self.layout.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
self.layout.image = UIGraphicsGetImageFromCurrentImageContext();
self.tmpLayout.image = nil;
UIGraphicsEndImageContext();
break;
}
default:
break;
}
}

53. - (void)clearScreen
{
UIGraphicsBeginImageContext(self.layout.frame.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(ctx, 255.0, 255.0, 255.0, 1.0);
CGContextFillRect(ctx, CGRectMake(0, 0,
self.tmpLayout.frame.size.width, self.tmpLayout.frame.size.height));
self.layout.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}

54. Video Shared whiteboard

56. All together

57. 'simple sync' example
· n-devices.
· Create a hash by each register based
in time.
· First sync in batch using a file.
· NSOutputstream to send 'ligth data'.
· Off and on send counters & timers
using MCSessionSendDataReliable.

58. 'simple sync' example
· n-devices.
· Create a hash by each register based
in time.
· First sync in batch using a file.
· NSOutputstream to send 'ligth data'.
· Off and on send counters & timers
using MCSessionSendDataReliable.

60. Ensembles1
"Sync for Core Data Apps"
1 http://www.ensembles.io

61. How far can I ...

62. How far can I ...
- RADIOUS2.
- DevRocket3
...
2 RADIOUS: https://itunes.apple.com/nz/app/radious-walkie-talkie/
id738480541?mt=8.
3 DeckRocket: https://github.com/jpsim/DeckRocket.

63. Questions
?

64. Thanks @patoroco