P2P communicationP2P communication

Using the GTalk Service APIUsing the GTalk Service API

IntroductionIntroduction• Peer-to-Peer communication highly used in

mobile devices.

• Very efficient to when certain factors such as battery, mobility and any other external costs are considered.

• Short Message Service (SMS)?– Ideal for two very remote devices (satellite?)– Slow– Expensive– Might not carry enough data into one SMS (even

more expensive)

GTalkServiceGTalkService BasicsBasics• Very similar to the Java Listener and Handler

technique• Mainly consists of:

– Several Intents• used to send/receive data• initialize the service connection

– A class implementing the ServiceConnection interface• Used once the connection is established

– A class extending the IntentReceiver abstract class• Used when the message is received

– An IGTalkService• Used to extract a GTalk session (IGTalkSession)

– An IGtalkSession• Used to send the data using sendMessage(String, Intent)

ServiceConnection-implementing classServiceConnection-implementing class

• Must be implemented to specify what to do during certain connection events

• Two methods– onServiceConnected(ComponentName, IBinder)

• Invoked by the Android platform once the requested service connection is established

– onServiceDisconnected(ComponentName)• Invoked by the Android platform once the connection is

lost (legally/illegally)

ServiceConnection continued …ServiceConnection continued …

• onServiceConnected(ComponentName name, IBinder service)1. IGTalkService gtalk_service =

IGTalkService.Stub.asInterface(service);

2. IGTalkSession session = gtalk_service.getDefaultSession();

• onServiceDisconnected(ComponentName name)1. Session = null; //no point in keeping

a non-connected session instance

Main procedureMain procedure• Initialize two instances (more on these later on):

– A ServiceConnection, and– An IntentReceiver

• Request a GTalk Service by binding it to your Activity– Create a new Intent– Set the Intent’s component to

GTalkService.GTALK_SERVICE_COMPONENT– Bind the intent using bindService(Intent, ServiceConnection,

int);

• Register the IntentReceiver using registerReceiver(IntentReceiver, IntentFilter)

• The platform will automatically invoke the onServiceConnected(ContextName, IBinder) method

Sending a message…• Using the recently extracted session, use the

sendMessage(String, Intent);– Intent msg = new Intent();– msg.setAction(GTalkDataMessageReceiver.ACTION);//to be explained on the next slide

– msg.putExtra(“1”, “Line 1”);– msg.putExtra(“2”, 34);– session.sendDataMessage(“john.doe”, msg);

IntentReceiver – abstract class• Must implement one particular abstract method:

onReceiveIntent(Context, Intent)– Invoked by the Android platform once an intent is

received from some external entity– Passes the Intent which was sent by the sender– Must make sure the incoming Intent is a GTalk

message sent by the sender

IntentReceiver continued …IntentReceiver continued …• onReceiveIntent(Context context, Intent

intent)1. if

(intent.getAction().equals(GTalkDataMessageReceiver.ACTION)) {//point 2}

2. Bundle b = intent.getExtras();

3. b.getString(“1”); //returns “Line 1”

4. b.getInt(“2”); //returns 32