1. Android Introduction
Hello Threads

2. Goal
Create a basic chat application that uses broadcast UDP to send and receive messages on the local network (75%)
Improve the chat application (25%)
You: Your text

3. Layout ListView showing both the messages sent as well as received
You: Your text
ListView showing
both the messages sent as
well as received
EditText allowing users
to enter text to be sent
Send button – sends the text

4. Application Structure
ServerThread
Main Activity
Constructor
Open the Socket
If successful – “Server Started”
Find the broadcast IP Address
Find the IP Address
OnCreate( )
Create the thread
Start the thread
run( )
while (socketStillOpen){
receive packet
display Message
send reply }
Message
Handler
OnDestroy( )
close the socket
sendPacket( )
send UDP
OnClickListener( )
Send Message

5. Main Activity (HelloThreads)
ClassMembers
EditText msg; // For typing the message
Button send; // For sending the message
ListView msgList; // For displaying the message list
ArrayAdapter <String>receivedMessages; // Holds the list of messages
ServerThread myThread; // The server thread handling all networking
Handler myHandler Similar to the one in HelloThreads
OnCreate( )
Get handles (findViewById) to all GUI elements
msgList = (ListView)findViewById(R.id.msgList);
receivedMessages = new ArrayAdapter<String>(this, R.layout.message);
msgList.setAdapter(receivedMessages);
Create ServerThread: myThread=new ServerThread(getApplicationContext(),mHandler)
Start the Thread: myThread.start();
Register the OnClickListener for the Send Button
OnDestroy( )
OnClickListener( )
case PACKET_CAME:
String incomingMessage = (String) msg.obj;
receivedMessages.add("You: "+incomingMessage);

6. ServerThread public class ServerThread extends Thread Class Members
Handler mHandler; // Handler for messages in the main thread
Context mContext; // Context to the application (for getting ip Addresses)
DatagramSocket serverSocket; // Socket used both for sending and receiving
boolean socketOK=true; // True as long as we don't get socket errors
InetAddress myBcastIPAddress; // my broadcast IP addresses
InetAddress myIPAddress; // my IP addresses
public ServerThread(Context currentContext,Handler handler){
mContext = currentContext;
mHandler = handler;
try
serverSocket = new DatagramSocket(PORT);
serverSocket.setBroadcast(true); ... catch and handle the exception
try getMyWiFiBcastAndIPAddress(); ... catch and handle the exception
run( ) – similar to HelloThreads, without the reply
sendPacket(String msg) – similar to UDP sender in HelloSockets

7. Getting the IP Address: getMyWiFiBcastAndIPAddress( );
WifiManager mWifi = (WifiManager) (mContext.getSystemService(Context.WIFI_SERVICE)); WifiInfo info = mWifi.getConnectionInfo(); DhcpInfo dhcp = mWifi.getDhcpInfo(); int myIntegerIPAddress = dhcp.ipAddress; int myIntBroadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask; byte[] quads = new byte[4]; for (int k = 0; k < 4; k++) quads[k] = (byte) ((myIntegerIPAddress>> k * 8) & 0xFF); try{ InetAddress myIPAddress = InetAddress.getByAddress(quads); return myIPAddress; }catch(Exception e){ if(D) Log.e(TAG,"Cannot Get My Own IP Address"); return null }

8. Improvements Your choice of examples – below are only examples
Different improvements are worth different amount of points
Max points 125%
Examples (only examples – go wild!):
Add names to the messages
Add images
Add voice
Add preferences
Handle Application lifecycle (on restart, on pause, on resume, etc.)
Vibrate or notify on receipt of a new message
Handle landscape/portrait
Localize it
Looks (background, icon, button, etc.)
Make utility for saving all messages in a file