S12 Near Field Communcations and Bluetooth

M12: Near Field

Communications and

Bluetooth

This App This App

Andy Wigley | Microsoft Technical Evangelist

Rob Tiffany | Microsoft Enterprise Mobility Strategist

Target Agenda | Day 1

Module and Topic | 10-minute breaks after each session / 60-minute “meal break” Planned

Duration

1a - Introducing Windows Phone 8 Application Development | Part 1 50:00

1b - Introducing Windows Phone 8 Application Development | Part 2 50:00

2 - Designing Windows Phone Apps 50:00

3 - Building Windows Phone Apps 50:00

4 - Files and Storage on Windows Phone 8 50:00

Meal Break | 60-minutes 60:00

5 - Windows Phone 8 Application Lifecycle 50:00

6 - Background Agents 25:00

7 - Tiles and Lock Screen Notifications 25:00

8 - Push Notifications 30:00

9 - Using Phone Resources on Windows Phone 8 50:00

Target Agenda | Day 2

Module and Topic | 10-minute breaks after each session / 60-minute “meal break” Planned

Duration

10 - App to App Communication 35:00

11 - Network Communication on Windows Phone 8 50:00

12 - Proximity Sensors and Bluetooth 35:00

13 - Speech Input on Windows Phone 8 35:00

14 - Maps and Location on Windows Phone 8 35:00

15 - Wallet Support 25:00

16 - In App Purchasing 25:00

Meal Break | 60-minutes 60:00

17 - The Windows Phone Store 50:00

18 - Enterprise Applications in Windows Phone 8: Architecture and Publishing 50:00

19 - Windows 8 and Windows Phone 8 Cross Platform Development 50:00

20 – Mobile Web 50:00

• Local Communication with Windows Phone

• Bluetooth Overview

• Using Bluetooth from an application

• Near Field Communications (NFC)

• Using NFC from an application

Agenda

• Local Communication is new to Windows Phone 8

• In Windows Phone 7 processes had to communicate using network connections

• This was difficult because programs had to determine the required IP address

• In Windows Phone 8 there are two new local communication methods available

• Bluetooth

• Can be used for phone to phone and phone to device communication over a range of

up to 10 meters

• Near Field Communication (NFC)

• Can be used for phone to device communication in very close proximity

Local Communication with Windows Phone 8

Bluetooth

• Bluetooth is a short range wireless communication technology

• Nominally the range is up to 10 metres, but this can be reduced by the conditions

• There are two Bluetooth communication scenarios supported by Windows Phone

• App to device

• A program running on Windows Phone can establish connection to an external device

• The Windows Phone must be paired with the device

• App to app

• A program running on a Windows Phone can find another application that is offering a

service that the device wishes to use; In this situation pairing is not required

• The Bluetooth connection is provided to the program in the form of a StreamSocket

Bluetooth Scenarios

• For App-to-Device scenarios, the device must have been paired with the phone

• A device must be made “discoverable” before pairing can take place

• Pairing is normally performed via the settings screen on the device

• During the pairing the connection is authenticated

• The user may need to enter a key to validate the connection

• This may be a fixed key, as in the case of devices such as headsets, or generated by one

device and entered on the other

• In an App-to-App Bluetooth connection, one app is looking for another instance of itself

on another phone

• Can communicate without needing to be paired

Bluetooth Pairing

• An application running on a Windows Phone 8 device

can obtain an enumeration of all the Bluetooth devices

that have been paired with the phone

• The application can then attempt to make a connection

to the required service on

that device

• For this to work the Bluetooth service on the phone

must be turned on

• The ID_CAP_PROXIMITY and ID_CAP_NETWORKING

capabilities must be enabled for the application to

make use of the Bluetooth communications to a device

App to Device

• The PeerFinder class can be used to search for paired devices

•

• The search will fail with the exception shown above if Bluetooth is switched off

Finding Paired devices

try { PeerFinder.AlternateIdentities["Bluetooth:Paired"] = ""; var peers = await PeerFinder.FindAllPeersAsync(); } catch (Exception ex) { if ((uint)ex.HResult == 0x8007048F) MessageBox.Show("Bluetooth is switched off"); }

• If the user needs to turn Bluetooth on the application can open the appropriate Settings

page using the ConnectionSettingsTask launcher

• Alternatively, use the LaunchUriAsync method:

Enabling Bluetooth

ConnectionSettingsTask connectionSettingsTask = new ConnectionSettingsTask(); connectionSettingsTask.ConnectionSettingsType = ConnectionSettingsType.Bluetooth; connectionSettingsTask.Show();

Windows.System.Launcher.LaunchUriAsync(new Uri("ms-settings-bluetooth"));

• A call to FindAllPeersAsync will return a list of PeerInformation values, each of

which describes a paired device that was discovered

• This includes a display name for the host, the name of the service it provides and a

HostName value which gives more detail about the device

• If no peers are found the list is empty , with a count of 0

Using the PeerInformation returned from PeerFinder

StringBuilder list = new StringBuilder(); foreach (PeerInformation p in peers) { list.AppendLine(p.DisplayName); }

• The ConnectAsync method will set up a StreamSocket that connects to a particular

service on the device

• The application must search for the service that it wishes to interact with

• The example below just connects to the service provided by the first peer found

• The method will throw an exception if either parameter is null or empty

Connection to a remote device

// Just use the first Peer PeerInformation partner = peers[0]; // Attempt a connection StreamSocket socket = new StreamSocket(); await socket.ConnectAsync(partner.HostName, partner.ServiceName);

• The Bluetooth discovery and connection methods provide the raw ability to transfer data

between the devices

• This is the StreamSocket that is created as part of the setup process

• The application will have to implement the communications protocol that is required for a

particular device

• Messages in this format will need to be exchanged between the application and

the device

Interacting with Remote Devices via Bluetooth

• App to App communication allows two programs to interact using Bluetooth to exchange

messages

• An application can wait for and respond to messages from

another application

• The PeerFinder class exposes an event which is raised when

a communication request is received from another system

• The communication is still performed using a SocketStream

that links the two programs

• The devices do not need to be paired in order to implement app to app connection

• The ID_CAP_PROXIMITY capability must be enabled

App to App communication

• An application can advertise itself as accepting connections by setting the display name

for the PeerFinder and then starting to advertise the service

• Note that doing this for a long time may have an adverse effect on battery life

Advertising a Service for other Applications

// Register for incoming connection requests PeerFinder.ConnectionRequested += PeerFinder_ConnectionRequested; // Start advertising ourselves so that our peers can find us PeerFinder.DisplayName = "PSR"; PeerFinder.Start();

• An application can subscribe to the ConnectionRequested event

• When the event fires the application can then decide whether to accept the request

• It could display a confirmation dialog to the user

Waiting for an Incoming Connection

// Register for incoming connection requests PeerFinder.ConnectionRequested += PeerFinder_ConnectionRequested; // Start advertising ourselves so that our peers can find us PeerFinder.DisplayName = "PSR"; PeerFinder.Start();

• The above method creates a connection to an incoming request from “RobsPhone”

• It uses the PeerInformation property of the ConnectionRequestedEventArgs to

determine who is attempting to connect

Responding to a Connection Request

StreamSocket socket; async void PeerFinder_ConnectionRequested(object sender, ConnectionRequestedEventArgs args) { if ( args.PeerInformation.DisplayName == "RobsPhone" ) { socket = await PeerFinder.ConnectAsync(args.PeerInformation); PeerFinder.Stop(); } }

• This checks the name of the incoming request and only responds to messages from

“RobsPhone”

• The application could instead display a confirmation dialog for the user that identifies

the source of the request



• This statement creates the socket

• In a complete application there should be a handler for any exceptions that this action

might produce



• This statement stops the phone from advertising the connection to other devices

• This will prevent further requests and also improve power consumption



• This method will read a string of text from the stream socket

• The message is read as a length value, followed by that number of characters

Application to Application Communication

private DataReader dataReader; private async Task<string> GetMessage() { if (dataReader == null) dataReader = new DataReader(socket.InputStream); await dataReader.LoadAsync(4); uint messageLen = (uint)dataReader.ReadInt32(); await dataReader.LoadAsync(messageLen); return dataReader.ReadString(messageLen); }

• This is the DataReader that will be used to extract information from the StreamSocket



• This is the DataReader that will be used to extract information from the StreamSocket

• The DataReader is created the first time the method is called



• This statement loads 4 bytes from the input stream



• This statement loads 4 bytes from the input stream

• The incoming 4 bytes are converted into an integer, which is the number of bytes that are

being transferred



• This statement loads the text of the string

• It uses the value that was supplied as the length



• This statement loads the text of the string

• It uses the value that was supplied as the length

• Once the bytes have been received, they’re converted into a string that is returned by the task



• This GetMessage method is a Task which can be started using the await keyword as

shown above

• When the task completes the message will be set to the received string

Initiating the Read

string message = await GetMessage();

• The SendMessage method is given a string that it sends to output stream

• It uses a DataWriter to format the output

Writing the message

DataWriter dataWriter; private async void SendMessage(string message) { if ( dataWriter == null) dataWriter = new DataWriter(socket.OutputStream); dataWriter.WriteInt32(message.Length); await dataWriter.StoreAsync(); dataWriter.WriteString(message); await dataWriter.StoreAsync(); }

• The dataWriter is created from the socket if it does not already exist

Writing the message


• The first item that is written is the length of the string

Writing the message


• The first item that is written is the length of the string

• This is followed by the string data itself

Writing the message


• This message transmitter method is not implemented as an awaitable

• It can just be called when the message is to be sent

Writing the message


• The SendMessage and GetMessage methods implement each end of a simple protocol

that serialises a message between the sender and the receiver

• If you want to send more complex data you can make use of appropriate serialisation

techniques to assemble the message text, just as you would between any processes which

are each end of a data channel

Messages and Protocols

demo

Bluetooth

App to App communication

over Bluetooth

• It is not possible to use the emulator to debug a program that uses Bluetooth

• An application can check to determine if the emulator is being used and

behave appropriately

Creating Bluetooth Solutions

if (Microsoft.Devices.Environment.DeviceType == Microsoft.Devices.DeviceType.Emulator) { MessageBox.Show("No Bluetooth on the emulator"); }

Near Field

Communications

(NFC)

• Near Field Communications provide a connection between devices that are very close

together (within 3-4 centimetres)

• The data is transferred at a rate of up to 424 Kbits/second

• It is assumed that this data transfer is intentional so there is not normally any

authentication as such

• The user has positioned their device close to the other device

• The phone can connect to an unpowered NFC chip/tag

Near Field Communications

• NFC is best for sending small amounts of data between devices and can be used in a

number of different scenarios:

• Connect devices.

• Initiate a Bluetooth or WiFi Direct connection to your app on another device

• Acquire content

• read “smart” posters that contain digital content in an embedded NFC tag

• Exchange digital objects

• exchange an electronic business card, or vCard.

Using Near Field Communications

• There are two ways that an application can use NFC

• Simple transfer of a message from one device to another

• An application can subscribe to message events and receive a string message of a

particular type

• An NFC connection can be used to configure a connection which is implemented using

Bluetooth or WiFi

• This extends the PeerFinder to allow an application to use NFC to quickly set up a

StreamSocket between two devices

Using NFC in applications

• It is very easy to publish a message to NFC

• Messages have a messagetype and a payload

• The PublishMessage method returns an ID value that uniquely identifies the message that was sent

• Messages are delivered to all applications that have subscribed to the message type

• The PublishMessage method can only be used where the message type begins with “Windows.”

• To publish messages by using another message type, like “WindowsMime.” or “NDEF:WriteTag”,

you must use the PublishBinaryMessage method

Publishing a Message

ProximityDevice device = ProximityDevice.GetDefault(); // Make sure NFC is supported if (device!= null) { long id = device.PublishMessage("Windows.JumpStartMessageType", "Hello From Rob!"); }

• The message is published everytime an NFC connection with another device is created,

until you stop publishing that message

• Messages continue to be published until the StopPublishingMessage method is called

or the ProximityDevice object is released

Stop Publishing a Message

private void StopPublishingMessage(object sender, RoutedEventArgs e) { device.StopPublishingMessage(publishedMessageId); publishedMessageId = -1; }

• The SubscribeForMessage method is given the message type and a delegate

• In the above code the message type is “Windows.JumpStartMessageType”

• You can add your own message types for your particular solution

Subscribing to Messages

ProximityDevice device = ProximityDevice.GetDefault(); // Make sure NFC is supported if (device!= null) { long id = device.SubscribeForMessage ("Windows.JumpStartMessageType", messageReceived); }

• When a message is received the event is raised and the program can make use of the

received data

• This event is fired when the received message has the same type

• In the case of our program it will fire when a message of type

“Windows.JumpStartMessageType” is received

Receiving Messages

private void messageReceived(ProximityDevice sender, ProximityMessage message) { Dispatcher.BeginInvoke(()=> MessageBox.Show("Message received " + message.DataAsString + " from " + sender.DeviceId) ); }

• If an application no longer wishes to subscribe to messages it can use the

StopSubscribingForMessage method to request this

• The method is provided with the message id that was returned when the subscription was

first set up

• An application may need to store this value in in case it is made dormant or tombstoned

when using Near Field Communications

Ending a subscription

device.StopSubscribingForMessage(id);

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7

demo

NFC

Exchanging small payload of data on Tap

• In this usage, the PeerFinder class is used to search for other instances of itself on the

tapped device

Finding a Windows Phone Peer App using NFC

ProximityDevice device = ProximityDevice.GetDefault(); // Make sure NFC is supported if (device != null) { PeerFinder.TriggeredConnectionStateChanged += OnTriggeredConnectionStateChanged; // Start finding peer apps, while making this app discoverable by peers PeerFinder.Start(); }

• Set the PeerFinder.AlternateIdentities property to allow connections to the Windows 8

version of your app

Finding a Windows 8 Peer App using NFC

ProximityDevice device = ProximityDevice.GetDefault(); // Make sure NFC is supported if (device != null) { PeerFinder.TriggeredConnectionStateChanged += OnTriggeredConnStateChanged; // Include the Windows 8 version of our app as possible peer PeerFinder.AlternateIdentities.Add("Windows", "my Win8 appID"); // Start finding peer apps, while making this app discoverable by peers PeerFinder.Start(); }

• The event arguments contain a state change message

Setting up a StreamSocket using NFC

void OnTriggeredConnStateChanged(object sender, TriggeredConnectionStateChangedEventArgs args) { switch (args.State) { case TriggeredConnectState.Listening: // Connecting as host break; case TriggeredConnectState.PeerFound: // Proximity gesture is complete – setting up link break; case TriggeredConnectState.Connecting: // Connecting as a client break; case TriggeredConnectState.Completed: // Connection completed, get the socket streamSocket = args.Socket; break; case TriggeredConnectState.Canceled: // ongoing connection cancelled break; case TriggeredConnectState.Failed: // Connection was unsuccessful break; } }

• The StreamSocket will be created using WiFi or Bluetooth to transfer the data

• An application can configure the networking technologies by setting these properties

• They are both set to true by default

• Note that for a successful infrastructure network connection both devices must be

connected to the same subnet and be able to directly connect each other

• It is advisable to make sure that Bluetooth is switched on before using this mechanism,

otherwise it might not be possible for the devices to connect in this way

• Note that WiFi Direct is not supported on Windows Phone 8

Using the connection

PeerFinder.AllowBluetooth = true; PeerFinder.AllowInfrastructure = true;

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NFC and Bluetooth

Setting up a Bluetooth StreamSocket using NFC Tap to

Connect

• An application running on a Windows Phone device can be interrupted at any time

• An incoming phone call, text message or the user pressing the Start button will cause

the application to be made dormant and possibly tombstoned

• When an application is made dormant all active network connections are disconnected as

it is no longer able to run in response to incoming messages

• However, Windows 8 provides a reconnection feature that an application can use to

quickly re-establish a connection that was disrupted in this way

• An application can persist connection configuration values that allows the socket to be

recreated when it resumes

Recreating a Connection

• The statements above persist the RawName and RemoteServiceName properties of a socket

into the state storage for an application

• If the application is resumed this information can be used to recreate the network

connection without having to make a new socket

• This information could be stored in isolated storage if you wanted to make the application

re-establish the connection when it is launched

• Need to be mindful of timeouts in this situation

Persisting connection information

PhoneApplicationService.Current.State["RemoteHostName"] = socket.Information.RemoteHostName.RawName; PhoneApplicationService.Current.State["RemoteServiceName"] = socket.Information.RemoteServiceName;

• When the application restarts it can recreate the connection by using the storage names

• Both of the parties in the socket based connection should use this to allow them to

recover network connections

• However, this option is not present on Windows 8, only on Windows Phone 8

Recreating a Socket

string storedRemoteHostRawName = PhoneApplicationService.Current.State["RemoteHostName"] as string; string storedRemoteServiceName = PhoneApplicationService.Current.State["RemoteServiceName"] as string; HostName newRemoteHostName = new HostName(storedRemoteHostRawName); await socket.ConnectAsync(newRemoteHostName, storedRemoteServiceName);

• Bluetooth and Near Field Communications (NFC) allow two Windows Phones to create

connections to each other and other devices

• To connection a Bluetooth device it must be paired with the phone and support the service

that the application requests

• Two applications can discover each other and exchange messages without pairing

• The connection provided is surfaced as a StreamSocket

• NFC allows a phone to exchange small amounts of data with another phone or device

Summary

• Windows Phone 8 provides a means by which an NFC message can be used to instigate

a StreamSocket connection over Bluetooth or WiFi between two devices

• Applications can store socket properties that allow connections to be resumed quickly

if the program is made dormant or tombstoned.

Summary continued

The information herein is for informational

purposes only an represents the current view of

Microsoft Corporation as of the date of this

presentation. Because Microsoft must respond

to changing market conditions, it should not be

interpreted to be a commitment on the part of

Microsoft, and Microsoft cannot guarantee the

accuracy of any information provided after the

date of this presentation.

© 2012 Microsoft Corporation.

All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.

MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION

IN THIS PRESENTATION.

Documents

S12 Near Field Communcations and Bluetooth