1 Android Introduction Hello Threads

2 Goal Create an application that uses a background thread as a UDP server to receive messages from the UDP client Text sent from UDPClient

3 Layout Text sent from UDPClient TextView that changes from Starting Server to Server Started (optional) TextView that shows the text sent from UDPClient TextView that shows the IP address of the server (needed for UDPClient) Clear Button – clears the Last Message (and shows that interface is still responsive)

4 Application Structure Main Activity ServerThreadUDPClient OnCreate( ) Create the thread Start the thread OnDestroy( ) close the socket Constructor Open the Socket If successful – Server Started Find and display the IP Address run( ) while (socketStillOpen){ receive packet display Message send reply } Read line from input Send line to Server Receive line from Server Display line OnClickListener( ) Clear the Last Message Message Handler HelloThreadsUDPClient

5 Main Activity (HelloThreads) ClassMembers TextView isRunning,myIPAddressField,lastMessage; Buttonclear; ServerThread myThread; Handler OnCreate( ) Get handles (findViewById) to all GUI elements Create ServerThread: myThread=new ServerThread(getApplicationContext(),mHandler) Start the Thread: myThread.start(); Register the OnClickListener for the Clear Button OnDestroy( ) myThread.closeSocket(); OnClickListener( ) Clear the Last Message Handler Definition on Next page

The Handler Definition private final Handler mHandler = new Handler() { public void handleMessage(Message msg) { switch (msg.what) { case PACKET_CAME: String incomingMessage = (String) msg.obj; lastMessage.setText(incomingMessage); break; case IS_RUNNING: String socketStatus = (String) msg.obj; isRunning.setText(socketStatus); break; case IP_ADDRESS: InetAddress myIPAddress = (InetAddress) msg.obj; myIPAddressField.setText("Server IP Address:"+myIPAddress.toString()); break; } }; 6

7 ServerThread public class ServerThread extends Thread Class Members Handler mHandler; // link to the Message Handler Context mContext; // link to application context DatagramSocket serverSocket; // the UDP socket well receive at public ServerThread(Context currentContext,Handler handler){ mContext = currentContext; mHandler = handler; Open the socket; if successful mHandler.obtainMessage(HelloThreads2.IS_RUNNING, "Server Started").sendToTarget(); InetAddress myIP = getMyWiFiIPAddress(); mHandler.obtainMessage(HelloThreads2.IP_ADDRESS, myIP).sendToTarget(); public void closeSocket() serverSocket.close(); public void run() Allows the socket to be closed (call from OnDestroy()) On Next Page On Next Next Page

8 Getting the IP Address: getMyWiFiIPAddress( ); WifiManager mWifi = (WifiManager) (mContext.getSystemService(Context.WIFI_SERVICE)); WifiInfo info = mWifi.getConnectionInfo(); DhcpInfo dhcp = mWifi.getDhcpInfo(); int myIntegerIPAddress = dhcp.ipAddress; 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 }

9 ServerThread.run( ) boolean socketOK=true; // True as long as we don't get socket errors while(socketOK) { DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); try{ serverSocket.receive(receivePacket); /***..... Same as the UDP server ****/ mHandler.obtainMessage(HelloThreads2.PACKET_CAME,sentence). sendToTarget(); } catch (Exception e){ socketOK = false; }// try }// while(socketOK) To the Message Handler in the main Thread Blocks Handles multiple requests as long as the socket is OK

Android Manifest To be able to use the Internet (open sockets) and to read our own IP address (from the WiFi Manager): 10