Programming context aware Mobile Phones

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Programming context awareMobile Phones
Agenda Introduction to Bluetooth
Methods for connecting Importent classes
Service description
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Server Programming
A mobile application is often a combination of a
MIDlet and a server side program
Many technologies on the server side CGI, PHP,
ASP, JSP, , Servlets,
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N-Tier Applications

• Presentation Tier
  Business Logic Tier
• 
  Database Tier

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Bluetooth
a cable replacement technology
A standard/protocol for a small , cheap short
range (10 meter) radio communication to be
plugged into computers, printers, mobile phones,
etc.IEEE 802.15 www.bluetooth.org
(/spec)
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Bluetooth - characteristics

• Bluetooth is wireless and automatic.
• Bluetooth is inexpensive.
• The ISM band (2.4 GHz) that Bluetooth uses is
  regulated, but unlicensed.
• Bluetooth handles both data and voice.
• Signals are omni-directional and can pass
  through walls and briefcases.  
• Bluetooth is spread spectrum.

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Frequency Hopping
Source http//www.swedetrack.com/images/bluet11.h
tm
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Bluetooth, Infrared and WLAN

• Infrared is
• Line-of-sight (interference uncommon)
• One-to-one (msg. delivery reliable)
• WLAN (IEEE 802.11b) is
• Intended for large devices with lots of power and
  speed (11 Mbit/sec, 100 meter)
• WAN (Wireless) versus PAN (Personal)
• Point Bluetooth is intended to co-exist with
  WLAN not replace it

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Bluetooth applications

• File transfer
• Ad-hoc networking
• Device synchronization
• Peripheral connectivity
• Car kits (hand-free installations)
• Mobile payments

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Piconets and Scatternets
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Details

• A master and seven slaves (8 nodes)
• Master initiates communication
• Packets survive five transmission slots
• Time-division multiplexing scheme for full-duplex
  (master even, slave odd)
• Three power-save modes

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Bluetooth in J2ME
HTTP con (HttpConnection)Connector.open(url)
L2CAP (Bluetooth) con (L2CAPConnection)Connecto
r.open(url)
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Bluetooth Overview
Device Discovery
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Establishing a network conn.

• Inquire Device finds access points (ap)
• Page Synchronize device with ap
• Establish link LMP (Link Manager Protocol) does
• Discover services LMP uses SDP (Service
  Discovery Protocol) to find ap services
• Create L2CAP ch. Maybe use RFCOMM
• Authenticate Maybe prompt user
• Log in PPP if RFCOMM used
• Send and receive data (e.g. TCP/IP)

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Bluetooth Profiles Security

• Profiles
• Idea Ensure interoperability
• Generic Access Profile must be supported by a
  Bluetooth-enabled device
• Security
• Pseudo-random frequency hopping
• Authentication
• Encryption

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Bluetooth system requirements

• Certain profiles must be supported
• Communication layers of Bluetooth 1.1
• Bluetooth Control Center (BCC)
• Concurrent applications
• Sets parameters in Bluetooth stack
• May be native app. or group of settings
• OBEX in underlying system or API implementation

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Packages andApplication Programming

• javax.bluetooth
• javax.obex
• Five steps in application programming
• Stack initialization (vendor dependent)
• Device management
• Device discovery
• Service discovery
• Communication

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Device Management
... // init stack LocalDevice local
LocalDevice.getLocalDevice() String address
local.getBluetoothAddress() String name
local.getFriendlyName() ...
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Device Discovery (1)
DiscoveryAgent agent local.getDiscoveryAgent()
// place the device in inquiry mode boolean
complete agent.startInquiry()
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Device Discovery (2)
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Service Discovery
DiscoveryAgent agent local.getDiscoveryAgent()
class ServiceListener implements
DiscoveryListener public void
servicesDiscovered( int transID, ServiceRecord
servRecord) public void
inquiryCompleted( int discType )
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Service Records
Before a service can be discovered it must be
registered
public interface ServiceRecord A ServiceRecord
contains a set of service attributes, where each
service attribute is an (ID, value) pair. An
SDP Server maintains a Service Discovery Database
(SDDB) of service records that describe the
services on the local device. ServiceRecords
are made available to a client application via an
argument of the servicesDiscovered method of the
DiscoveryListener interface.
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Example

• // Create service record that represents the
  service
• StreamConnectionNotifier service
• (StreamConnectionNotifier) Connector.open(someUR
  L)
• // Obtain service record created by the server
  device
• ServiceRecord sr local.getRecord(service)
• // Indicate that service is ready to accept
  client conn.
• // acceptAndOpen() blocks until a client connects
• StreamConnection connection
• (StreamConnection) service.acceptAndOpen()
• // When ready to exit close connection and rem.
  Service
• service.close()

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Communication (L2CAP)
// L2CAP Logical Link Control and Adaption
P. L2CAPConnection con byte b con.send(b)
con.receive(b)
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Bluetooth Protocols
Source http//www.palowireless.com/infoto
oth/tutorial.asp
In J2ME API
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Bluetooth Example
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Device Discovery in J2ME (1)
DiscoveryAgent disc_agent local_device.getDiscov
eryAgent() inq_listener new
InquiryListener() disc_agent.startInquiry(
DiscoveryAgent.LIAC, inq_listener) Enumeration
devices inq_listener.cached_devices.elements()
/ LIAC Limited inquiry Access Code /
local_device.setDiscoverable
(DiscoveryAgent.NOT_DISCOVERABLE)
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Device Discovery in J2ME (2)
class InquiryListener implements
DiscoveryListener public Vector
cached_devices public InquiryListener()
cached_devices new Vector()
public void deviceDiscovered(
RemoteDevice btDevice, DeviceClass cod)
int major cod.getMajorDeviceClass()
if(! cached_devices.contains(btDevice))
cached_devices.addElement(btDevice)
public void inquiryCompleted( int discType )
synchronized(this) this.notify()
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Service Discovery
UUID u new UUID1 // UUID Universal Unique
ID u0 new UUID("00000000000010008000006057028A
06", false ) int
attrbs 0x0100 // UUID for L2CAP
serv_listener new ServiceListener()
while( devices.hasMoreElements() )
synchronized(serv_listener) / now find on
remote dev. / disc_agent.searchServices(att
rbs, u, (RemoteDevice)devices.nextEl
ement(), serv_listener) try
serv_listener.wait() catch(InterruptedException
e)
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Communication (1)
String url serv_listener.service.getConnectionUR
L(0, false) deviceName LocalDevice.getLocalDevi
ce().getFriendlyName() conn (L2CAPConnection)
Connector.open( url ) String s "Hello server,
my name is deviceName byte b
s.getBytes() try conn.send(b)
catch(IOException e)
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Communication (2)
byte b new byte1000 // actual
communication while (listening) if
(conn.ready()) conn.receive(b) String s
new String(b, 0, b.length)
System.out.println("received from server
s.trim()) listening false
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Source Code for Example
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Location Based Services
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L2CAP versus RFCOMM
L2CAP (packetss)
RFCOMM (serial)
00011010101010
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OBEX

• OBject EXchange
• Communication protocol, client/server
• Protocol stack
• Applications
• OBEX (OBject EXchange)
• SDP (Service Discovery) RFCOMM
• L2CAP (Logical Link Control and Adaption)
• HCI (Host Controller Interface), soft/hard
• LMP (Link Manager), link setup and piconet
• Baseband (control and send data packets)
• Radio (physical wireless connection, 79 ch.)

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OBEX usage

• Used to implement Bluetooth profiles
• Generic Object Exchange
• Object Push
• Synchronization
• File Transfer
• Basic Imaging
• Basic Printing
• Object model and Session protocol
• Objects have headers (e.g. HTTP)
• Request-Response (packets) e.g. CONNECT

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Communication example

• Client Connect request
• Contains operation, packet length, headers
• Server Success
• Contains response codelengthdata
• Client Put/Get
• Server Continue
• Client Put/Get
• Server Success
• Client Disconnect
• Server Success

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Code anyone?

• ClientSession session
• (ClientSession)Connector.open(connectURL)
• HeaderSet hdr clientSession.createHeaderSet()
• // Create header set to request Hello.txt file
  from server
• hdr.setHeader(HeaderSet.TYPE, text/vCard)
• hdr.setHeader(HeaderSet.NAME, Hello.txt)
• // OBEX server can retrieve them by calling
  getHeader()
• Operation op session.put(null)
• OutputStream out op.openOutputStream()
• out.write(Test.getBytes())
• out.close()
• if(op.getResponseCode() ResponseCodes.OBEX_HTTP
  _OK)
• System.out.println( PUT operation is
  success)

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Server side code

• Servers must implement a ServerRequestHandler and
  a SessionNotifier
• public int onGet(Operation op)
• try
• HeaderSet hdr op.getReceivedHeaders()
• SessionNotifier sn (SessionNotifier)
• Connector.open(btgoep//localhost1106nameFTP)
  
• sn.acceptAndOpen(serverRequestHandler)

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The PUT operation

• con (ClientSession)Connector.open(serviceURL)
• hdr con.connect(hdr) hdr con.createHeaderSet(
  )
• hdr.setHeader(HeaderSet.TYPE, text/plain)
• hdr.setHeader(HeaderSet.NAME, Hello.txt)
• Operation op con.put(hdr)
• // Sending the body
• OutputStream writeStrm op.openOutputStream()
• StreamConnection strmCon (StreamConnection)
• .open(file//name filename moder)
• InputStream readStrm strmCon.openInputStream()
• byte block new byte512 Int dataSize -1
• while ((dataSize readStrm.read(block)) ! -1)
• writeStrm.write(block, 0, dataSize)
• // Send END-OF-BODY-HEADER and close streams

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Relevant Links
Bluetooth API http//jcp.org/en/jsr/detail?id82
Toolkit extension (Nokia) Series 60 MIDP Concept
SDK Beta 0.3.1 http//www.forum.nokia.com/main.htm
l
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Break
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The Connector Class

• Used to open a Connection (interface)
• open(String name)
• open(String name, int mode)
• open(String name, int mode, boolean timeouts)
• name schemeaddressparameters
• (protocol, resource ids, xy)
• mode Connection attribute
• (READ, WRITE, READ_WRITE)
• timeouts Can application use timeouts
• (E.g. to prevent indefinite blocking)
• Which connection types can we open?

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Connection types

• The CLDC GCF (super)interface overview
• Connection
• InputConnection/OutputCon. (streams)
• StreamConnection (both I/O)
• SocketConnection
• SecureConnection (use ssl scheme)
• CommConnection (logical serial ports)
• HttpConnection (request-response protocol)
• HttpsConnection (use https scheme)
• StreamConnectionNotifier
• ServerSocketConnection
• DatagramConnection (discrete packets)
• UDPDatagramConnection (User Data Protocol)
• SecurityInfo
• PushRegistry Class

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Client/Server

• Algorithm for communication
• Build name and invoke Connectors open()
• Get output stream, send request to server
• Open input stream and read response
• Close both streams and the socket
• Clean up inside finally block to handle
  (communication) errors close I/O
• A server obtains a StreamConnectionNotifier
  object and calls acceptAndOpen() in a loop, this
  call returns with a StreamConnection object when
  a client connects

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Reading Data
InputStream in getClass().getResourceAsStream(/
large.txt) InputStreamReader r new
InputStreamReader(in)
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Reading Data Wirelessly
String url "http//www.itu.dk/courses/JMA/F2005/
large.txt"
InputStream in ((HttpConnection)Connector.open
(url)).openInputStream() while (...)
in.read(data)
import javax.microedition.io.HttpConnection im
port javax.microedition.io.Connector
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Example

• void getViaHttpConnection(String url) throws
• IOException
• HttpConnection c null
• InputStream is null
• int rc
• try
• // Get response code, opens connection,
• // send the request, and read the HTTP
• // response headers. The headers are
• // stored until requested.
• c (HttpConnection)Connector.open(url)
• rc c.getResponseCode()
• if (rc ! HttpConnection.HTTP_OK)
• throw new IOException("HTTP response code
  " rc)
• is c.openInputStream() // Get the
  ContentType
• String type c.getType()
• // process data