JMA F2005 Ebbe Elsborg [email protected] Programming context aware Mobile Phones Agenda: Introduction to Bluetooth Methods for connecting Importent classes

JMA F2005 Ebbe Elsborg [email protected]

Programming context awareMobile Phones

Agenda:

Introduction to Bluetooth Methods for connecting

Importent classes

Service description


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, …


N-Tier Applications

Presentation Tier – Business Logic Tier – Database Tier


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)


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.


Frequency Hopping

Source: http://www.swedetrack.com/images/bluet11.htm


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


Bluetooth applications

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


Piconets and Scatternets


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


Bluetooth in J2ME

HTTP:

con= (HttpConnection)Connector.open(url);

L2CAP (Bluetooth):

con= (L2CAPConnection)Connector.open(url);


Bluetooth Overview

Device Discovery

Service Discovery

Communication


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)


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


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


Packages andApplication Programming• javax.bluetooth• javax.obex

• Five steps in application programming:– Stack initialization (vendor dependent)– Device management– Device discovery– Service discovery– Communication


Device Management

... // init stack

LocalDevice local = LocalDevice.getLocalDevice();

String address = local.getBluetoothAddress();

String name = local.getFriendlyName();

...

RemoteDevice remote = RemoteDevice.getRemoteDevice(conn);


Device Discovery (1)

class InquiryListener implements DiscoveryListener { // Called each time a device is discovered public void deviceDiscovered(

RemoteDevice btDevice, DeviceClass cod) { … } // Called when inquiry is completed or cancelled public void inquiryCompleted( int discType ) { … } …}

DiscoveryAgent agent= local.getDiscoveryAgent();

// place the device in inquiry mode

boolean complete = agent.startInquiry();


Device Discovery (2)

DiscoveryAgent agent = local.getDiscoveryAgent();

// return an array of pre-known (cached) devices RemoteDevice[] devices= agent.retrieveDevices(DiscoveryAgent.CACHED);


Service Discovery

DiscoveryAgent agent = local.getDiscoveryAgent();

class ServiceListener implements DiscoveryListener { public void servicesDiscovered(

int transID, ServiceRecord[] servRecord) {

}

public void inquiryCompleted( int discType ) {

} …

}


Service Records

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.

Before a service can be discovered it must be registered


Example

// Create service record that represents the serviceStreamConnectionNotifier service = (StreamConnectionNotifier) Connector.open(”someURL”);

// Obtain service record created by the server deviceServiceRecord sr = local.getRecord(service);

// Indicate that service is ready to accept client conn.// acceptAndOpen() blocks until a client connectsStreamConnection connection = (StreamConnection) service.acceptAndOpen();

// When ready to exit close connection and rem. Serviceservice.close();


Communication (L2CAP)

// L2CAP: Logical Link Control and Adaption P.L2CAPConnection con;byte[] b

con.send(b);

con.receive(b);


Bluetooth Protocols

Source http://www.palowireless.com/infotooth/tutorial.asp

In J2ME API


Bluetooth Example

conn= (L2CAPConnection)Connector.open(url);

send("Hello server, my name is: "+getName());


Device Discovery in J2ME (1)

DiscoveryAgent disc_agent = local_device.getDiscoveryAgent();

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);

synchronized(inq_listener) { // to make wait possible

try {inq_listener.wait(); } catch(InterruptedException e){}

}


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(); }

}


Service DiscoveryUUID[] u = new UUID[1]; // UUID: Universal Unique ID

u[0] = new UUID("00000000000010008000006057028A06", 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(attrbs, u, (RemoteDevice)devices.nextElement(), serv_listener);

try {serv_listener.wait();} catch(InterruptedException e){}

} }


Communication (1)

String url = serv_listener.service.getConnectionURL(0, false);

deviceName = LocalDevice.getLocalDevice().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){};


Communication (2)

byte[] b = new byte[1000]; // 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;

}

}


Location Based Services

GPS (global)

Local (e.g. within buildings)

Cell based (within cities)


L2CAP versus RFCOMM

L2CAP(packetss)

RFCOMM(serial) 00011010101010


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.)


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


Communication example

• Client: Connect request– Contains operation, packet length, headers

• Server: Success– Contains response code+length+data

• Client: Put/Get• Server: Continue• Client: Put/Get• Server: Success• Client: Disconnect• Server: Success


Code anyone?

ClientSession session = (ClientSession)Connector.open(connectURL);

HeaderSet hdr = clientSession.createHeaderSet();// Create header set to request ’Hello.txt’ file from serverhdr.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”); }


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://localhost:1106;name=FTP”);sn.acceptAndOpen(serverRequestHandler);


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 bodyOutputStream writeStrm = op.openOutputStream();StreamConnection strmCon = (StreamConnection)

.open(”file://name=” + filename + ”;mode=r”);InputStream readStrm = strmCon.openInputStream();byte[] block = new byte[512]; Int dataSize = -1;while ((dataSize = readStrm.read(block)) != -1)

{ writeStrm.write(block, 0, dataSize); }… // Send END-OF-BODY-HEADER and close streams


Relevant Links

Bluetooth APIhttp://jcp.org/en/jsr/detail?id=82

Toolkit extension (Nokia):Series 60 MIDP Concept SDK Beta 0.3.1http://www.forum.nokia.com/main.html


Break


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: scheme:address;parameters (protocol, resource ids, x=y)

mode: Connection attribute (READ, WRITE, READ_WRITE)

timeouts: Can application use timeouts (E.g. to prevent indefinite

blocking)

• Which connection types can we open?


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


Client/Server

• Algorithm for communication– Build name and invoke Connector’s 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


Reading Data

InputStream in = getClass().getResourceAsStream(“/large.txt”);

InputStreamReader r = new InputStreamReader(in);


Reading Data Wirelessly

InputStream in = ((HttpConnection)Connector.open

(url)).openInputStream();

while (...) in.read(data);

+

import javax.microedition.io.HttpConnection;import javax.microedition.io.Connector;

String url = "http://www.itu.dk/courses/JMA/F2005/large.txt"


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

Documents

JMA F2005 Ebbe Elsborg [email protected] Programming context aware Mobile Phones Agenda: Introduction to Bluetooth Methods for connecting Importent classes