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Multipeer Networking ----------------- Rob Stearn

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History Overview Code ! Future

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History

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No content

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Overview

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Multipeer networking sends data from one device to many

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Multipeer networking sends data from one device to many requires no server infrastructure

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Multipeer networking sends data from one device to many requires no server infrastructure sends over Bluetooth, *Ad-Hoc or Infrastructure WiFi

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Multipeer networking sends data from one device to many requires no server infrastructure sends over Bluetooth, *Ad-Hoc or Infrastructure WiFi bridges across interfaces

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Consider 3 iOS devices...

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Consider 3 iOS devices...

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Consider 3 iOS devices...

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Consider 3 iOS devices... 1 connects to 2 via Bluetooth 3 connects to 2 via WiFi 1, 2 and 3 can all see each other no direct connection between 1 & 3 required

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Multipeer networking sends data from one device to many requires no server infrastructure sends over Bluetooth, *Ad-Hoc or Infrastructure WiFi bridges across interfaces can send data as Message, File or Stream

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Multipeer networking sends data from one device to many requires no server infrastructure sends over Bluetooth, *Ad-Hoc or Infrastructure WiFi bridges across interfaces can send data as Message, File or Stream can ensure order and delivery of data

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Multipeer networking sends data from one device to many requires no server infrastructure sends over Bluetooth, *Ad-Hoc or Infrastructure WiFi bridges across interfaces can send data as Message, File or Stream can ensure order and delivery of data API requires iOS7+

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Discovery

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Discovery Zero-configuration networking over IP

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Discovery Zero-configuration networking over IP Every peer acts as a DNS for itself

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Discovery Zero-configuration networking over IP Every peer acts as a DNS for itself Uses URLs with with the .local domain

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Discovery Zero-configuration networking over IP Every peer acts as a DNS for itself Uses URLs with with the .local domain Uses multicast DNS to discover services

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Discovery Zero-configuration networking over IP Every peer acts as a DNS for itself Uses URLs with with the .local domain Uses multicast DNS to discover services Peers self-assign an IP in the 169.254.xxx.xxx range

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Discovery APIs

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Code

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3 Objects: Session Browser Advertiser

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Session, Browser and Advertiser

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Session, Browser and Advertiser

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Session, Browser and Advertiser

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Session, Browser and Advertiser

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Session, Browser and Advertiser

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Session, Browser and Advertiser

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kMCSessionMaximumNumberOfPeers

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kMCSessionMaximumNumberOfPeers Bluetooth: 8

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kMCSessionMaximumNumberOfPeers Bluetooth: 8 Wi-fi: 8?

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Session Browser Advertiser Sending data

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Session / MCPeerID MCPeerID *peerID = [[MCPeerID alloc] initWithDisplayName:@"cocoad elica"];

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Session / Initialize self.session = [[MCSession alloc] initWithPeer:peerID securityIdentity:nil* encryptionPreference: MCEncryptionRequired**];

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Session / Initialize self.session = [[MCSession alloc] initWithPeer:peerID securityIdentity:nil* encryptionPreference: MCEncryptionRequired**]; * optional Array with SecIdentityRef and SecCertificateRef items

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Session / Initialize self.session = [[MCSession alloc] initWithPeer:peerID securityIdentity:nil* encryptionPreference: MCEncryptionRequired**]; * optional Array with SecIdentityRef and SecCertificateRef items ** choose from MCEncryptionRequired, MCEncryptionOptional or MCEncryptionNone

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Session / Delegate didChangeState: didReceiveCertificate: didReceiveData: didStartReceivingResourceWithName: didFinishReceivingResourceWithName: didReceiveStream:

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Session / Details Foreground operation only

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Session / Details Foreground operation only Disconnects on breakpoints

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Session / Details Foreground operation only Disconnects on breakpoints Good candidate for a singleton*

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Browser / Initialize MCBrowserViewController *bvc = [[MCBrowserViewController alloc] initWithServiceType:(NSString *)serviceType session:(MCSession *)session];

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Browser / Initialize MCBrowserViewController *bvc = [[MCBrowserViewController alloc] initWithServiceType:(NSString *)serviceType session:(MCSession *)session]; Use a 1-15 character string for service type Check IANA domain naming conventions

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Browser "Easy mode"

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Browser "Easy mode" boxed solution

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Browser "Easy mode" boxed solution minimal styling

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Browser "Easy mode" boxed solution minimal styling awesome!

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Browser "Easy mode" boxed solution minimal styling awesome! a bit dull

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Browser / Delegate MCBrowserViewControllerDelegate browserViewController:shouldPresentNearbyPeer :withDiscoveryInfo: browserViewControllerDidFinish: browserViewControllerWasCancelled:

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Browser / Details "Hard Mode" Build a custom UI Use MCNearbyServiceBrowser for data and callbacks

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Browser / 'Hard Mode' MCNearbyServiceBrowserDelegate didNotStartBrowsingForPeers: foundPeer:withDiscoveryInfo: lostPeer:

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Advertiser / Initialize [[MCAdvertiserAssistant alloc] initWithServiceType:service discoveryInfo:discoveryDict session:mySession];

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Advertiser / Initialize [[MCAdvertiserAssistant alloc] initWithServiceType:service discoveryInfo:discoveryDict session:mySession]; discoveryInfo is your opportunity to add additional info and context about your user.

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Advertiser / discoveryInfo NSDictionary Keys and Values must be of type NSString Max size per key/value pair of 256 bytes

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Advertiser / Details "Hard Mode" Build a custom UI for invitations Use MCNearbyServiceAdvertiser advertising & callbacks

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Advertiser / 'Hard Mode' MCNearbyServiceAdvertiserDelegate advertiser: didNotStartAdvertisingPeer: advertiser: didReceiveInvitationFromPeer: withContext: invitationHandler:

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Sending data Messages Resources Streams

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Messages Data with known bounds, serialized into NSData objects, sent atomically sendData: toPeers: withMode: error: session: didReceiveData: fromPeer:

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Messages can be sent as either: MCSessionSendDataReliable which guarantees delivery and order

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Messages can be sent as either: MCSessionSendDataReliable which guarantees delivery and order MCSessionSendDataUnreliable which does not

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Messages can be sent as either: MCSessionSendDataReliable which guarantees delivery and order MCSessionSendDataUnreliable which does not Analogy to TCP/UDP

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Resources Text files, File URLs or Web URLs sendResourceAtURL: withName: toPeer: withCompletionHandler: Callbacks to start and finish transfer, uses NSProgress

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Streams Unbounded data, uses NSStreams startStreamWithName: toPeer: error: returns an NSOutputStream session: didReceiveStream: withName: fromPeer: gives an NSInputStream

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Streams For both input and output streams: > Add stream to a run loop > Open the stream > Set a delegate and respond to stream: handleEvent: callback

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!

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Duplicates in the browser

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Duplicates in the browser Issue: MCPeerID created each time MCSession is instantiated

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Duplicates in the browser Issue: MCPeerID created each time MCSession is instantiated Solution: Each peer should serialize its own MCPeerID with NSKeyedArchiver, save it to disk and reuse for each new session.

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Invitation response times

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Invitation response times Issue: Once an invitation is accepted there's a delay before connecting

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Invitation response times Issue: Once an invitation is accepted there's a delay before connecting Solution: Encryption is on by default which adds overhead to initial connections. Consider using MCEncryptionNone

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Comparing MCPeerIDs

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Comparing MCPeerIDs Issue: MCPeerID hash method returns it's unique ID number, as an NSUInteger.

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Comparing MCPeerIDs Issue: MCPeerID hash method returns it's unique ID number, as an NSUInteger. Solution: Truncate the returned hash to 32-bit for comparison.

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Demo

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LocalTalk on the app store update in progress for iOS 8 OS X version to follow free!

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Future

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Multipeer for Mac

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Multipeer for Mac Common API with iOS

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Multipeer for Mac Common API with iOS But! Supports background operation

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Multipeer for Mac Common API with iOS But! Supports background operation However! Not Bluetooth

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Multipeer for Mac Common API with iOS But! Supports background operation However! Not Bluetooth AirDrop rebuilt to use the new API

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Multipeer for Mac Common API with iOS But! Supports background operation However! Not Bluetooth AirDrop rebuilt to use the new API OS X <-> iOS AirDrop. Finally.

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End created with Deckset http://www.decksetapp.com icons made with Sketch http://bohemiancoding.com/sketch/

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Questions?

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Rob Stearn @cocoadelica www.cocoadelica.co.uk [email protected]

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WWDC 2013 Session 708 WWDC 2014 Session 709 IANA service type list Bonjour Overview Multipeer Networking Reference NSNetServices & CFNetServices Programming Guide MultipeerGroupChat sample code Forums