Windows 8 Platform NFC Development

Windows 8 PlatformNFC DevelopmentAndreas Jakl [@mopius]nfcinteractor.comTechnology WizardNokia 1 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl NFC Forum and the NFC Forum logo are trademarks of the Near Field Communication Forum.

Tap and Do A gesture that is a natural interaction between people in close proximity used to trigger doing something together between the devices they are holding. System: Near Field Proximity (e.g., NFC)4 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl Documentation: bit.ly/ProximitySpec

Acquire Content Scenarios Laulujoutsen Whooper Swan Website link (e.g., company) National bird of Finland, on €1 coin bit.ly/PureWordPlay More information (e.g., museum, concert) Custom app extensions (e.g., bonus item for a game)6 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl Angry Birds © Rovio

Get Started: Read URIs via NFC ProximityDevice Connect to HW Detect devices in range Publish & subscribe to messages ProximityMessage Contents of received message7 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

URI Subscriptions1 Activate proximity device _device = ProximityDevice.GetDefault();2 Subscribe to URI messages _subscribedMessageId = _device.SubscribeForMessage( "WindowsUri", MessageReceivedHandler);3 Handle messages private void MessageReceivedHandler(ProximityDevice sender, ProximityMessage message) { var msgArray = message.Data.ToArray(); var url = Encoding.Unicode.GetString(msgArray, 0, msgArray.Length); Debug.WriteLine("URI: " + url); }9 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

URI Subscriptions Smart Poster WindowsUri URI4 Cancel subscriptions _subscribedMessageId = _device.SubscribeForMessage(…); _device.StopSubscribingForMessage(_subscribedMessageId);10 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

Publish URI Messages1 Start publishing _publishingMessageId = _device.PublishUriMessage( new Uri("http://nokia.com");• Proximity devices only – (doesn’t write tags)• Windows Protocol + URI record – Encapsulated in NDEF12 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

Write URI Tags1 Prepare & convert data var dataWriter = new Windows.Storage.Streams.DataWriter { UnicodeEncoding = Windows.Storage.Streams. UnicodeEncoding.Utf16LE}; Mandatory dataWriter.WriteString("http://nokia.com"); encoding var dataBuffer = dataWriter.DetachBuffer();2 Write tag (no device publication) _device.PublishBinaryMessage("WindowsUri:WriteTag", dataBuffer);13 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

Tag Size?1 Subscribe for writable tag info _device.SubscribeForMessage("WriteableTag", MessageReceivedHandler);2 Check maximum writable tag size in handler var tagSize = BitConverter.ToInt32(message.Data.ToArray(), 0); Debug.WriteLine("Writeable tag size: " + tagSize);3 Device HW capabilities var bps = _device.BitsPerSecond; // >= 16kB/s var mmb = _device.MaxMessageBytes; // >= 10kB14 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl API documentation: bit.ly/ProximityAPI

Data on an NFC Tag Smart PosterTitleThe JourneyURIjourney2.mopius.com Data Encapsulated in Encoded through Stored on NDEF Records NDEF Message NFC Forum NFC Forum Tag Tag Type Platform NDEF = NFC Data Exchange Format16 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl Container image adapted from s_volenszki (Flickr), released under Creative Commons BY-NC 2.0

Reading NDEF *1 Subscribe to all NDEF messages _subscribedMessageId = _device.SubscribeForMessage( "NDEF", MessageReceivedHandler);2 Parse raw byte array in handler  http://www.nfc-forum.org/specs/17 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl * For URI records + simple Smart Poster (w/o title), use the WindowsUri type

Reading NDEF *1 Subscribe to all NDEF messages // Convert the language code to a byte array assembling payload of Text record var languageEncoding = Encoding.UTF8; var encodedLanguage = languageEncoding.GetBytes(languageCode); _subscribedMessageId = _device.SubscribeForMessage( // Encode and convert the text to a byte array var encoding = (textEncoding == TextEncodingType.Utf8) ? Encoding.UTF8 : Encoding.BigEndianUnicode; "NDEF", MessageReceivedHandler); var encodedText = encoding.GetBytes(text); // Calculate the length of the payload & create the array var payloadLength = 1 + encodedLanguage.Length + encodedText.Length;2 Parse raw byte array in handler  Payload = new byte[payloadLength]; // Assemble the status byte Payload[0] = 0; // Make sure also the RFU bit is set to 0 // Text encoding if (textEncoding == TextEncodingType.Utf8) Simple example: Payload[0] &= 0x7F; // ~0x80 else http://www.nfc-forum.org/specs/ Payload[0] |= 0x80; // Language code length Payload[0] |= (byte)(0x3f & (byte)encodedLanguage.Length); // Language code Array.Copy(encodedLanguage, 0, Payload, 1, encodedLanguage.Length); // Text Array.Copy(encodedText, 0, Payload, 1 + encodedLanguage.Length, encodedText.Length);18 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl * For URI records + simple Smart Poster (w/o title), use the WindowsUri type

NDEF.codeplex.com Create NDEF Reusable Parse information messages & records NDEF from raw byte arrays (standard compliant) classes Fully documented Open Source LGPL license (based on Qt Mobility)20 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

Reading: Smart Poster// Parse raw byte array to NDEF messagevar msg = NdefMessage.FromByteArray(rawMsg);foreach (NdefRecord record in msg){ // Go through each record, check if its a Smart Poster if (record.CheckSpecializedType() == typeof (NdefSpRecord)) { // Convert and extract Smart Poster info var spRecord = new NdefSpRecord(record); Debug.WriteLine("URI: " + spRecord.Uri); Debug.WriteLine("Titles: " + spRecord.TitleCount()); Debug.WriteLine("1. Title: " + spRecord.Titles[0]); Debug.WriteLine("Action set: " + spRecord.ActionInUse());} }21 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

Writing: Smart Poster// Initialize Smart Poster record with URI, Action + 1 Titlevar spRecord = new NdefSpRecord { Uri = "http://nokia.com", NfcAction = NdefSpActRecord.NfcActionType.DoAction };spRecord.AddTitle(new NdefTextRecord { Text = "Nokia", LanguageCode = "en" });// Add record to NDEF messagevar msg = new NdefMessage { spRecord };// Publish NDEF message to a tag / phone_device.PublishBinaryMessage("NDEF:WriteTag", msg.ToByteArray().AsBuffer());22 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

App Launching Register for URI LaunchApp Peer to Files protocol Tag Peer User opens Tag launches app Tag directly contains App requests peer particular file through custom app name and device to start URI scheme parameters the same app Not so relevant for NFC25 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

URI Protocol nfcinteractor: compose Protocol Custom name data Encoded Launch URI Examples* skype:mopius?call spotify:search:17th%20boulevard26 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl * Definition & more examples: http://en.wikipedia.org/wiki/URI_scheme

LaunchApp Tagparameters a b t platform 1 t a b app name 1 b t a platform 2 a b t app name 2 … Encoded into NDEF message* Directly launch App27 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl * For your low-level interest: type: Absolute URI, type name format: windows.com/LaunchApp. Contents re-formatted, e.g., with string lengths before each value

Peer to Peer Tap for Quick Data Long Term Exchange Connection ProximityDevice PeerFinder Exchange Windows / Automatically builds NDEF messages, Bt / WiFi Direct SNEP protocol socket connection29 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

Connection State Proximity gesture complete 1 Devices can be pulled away PeerFound Which device initiated tap gesture? → Connecting, other device Listening 2 Connecting / Listening Access socket of persistent transport (e.g., TCP/IP, Bt) 3 Completed31 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl

Find Peers1 Start waiting for triggered connections PeerFinder.TriggeredConnectionStateChanged += TriggeredConnectionStateChanged; PeerFinder.Start();2 Peer found & connection established? Send message over socket private async void TriggeredConnectionStateChanged(object sender, TriggeredConnectionStateChangedEventArgs eventArgs) { if (eventArgs.State == TriggeredConnectState.Completed) { // Socket connection established! var dataWriter = new DataWriter(eventArgs.Socket.OutputStream); dataWriter.WriteString("Hello Peer!"); var numBytesWritten = await dataWriter.StoreAsync(); }} 332 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl Completed * For URI records + simple Smart Poster (w/o title), use the WindowsUri type. API documentation: bit.ly/ProximityAPI

UX Recommendations*User initiated peer Show connection Ask for consent search only stateFailed connection? Let user get out of Proximity: only ifInform & revert to proximity connection details single-user mode experience not relevant33 © 2012 Nokia Windows 8 Platform NFC Development v1.0.0p September 11, 2012 Andreas Jakl * bit.ly/ProximityUX

Windows 8 Platform NFC Development

by Andreas Jakl on Sep 12, 2012

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