UDP with android

UDP with android

why UDP Android just once send [Please Help]
name class MainActivity
public class MainActivity extends Activity implements
android.view.View.OnClickListener { public static final String SERVERIP =
"192.168.5.255"; public static final int SERVERPORT = 4444; public
TextView text1; public EditText input; public Button btn; public boolean
start; public Handler Handler; static boolean isFinish = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text1 = (TextView) findViewById(R.id.textView1);
input = (EditText) findViewById(R.id.editText1);
btn = (Button) findViewById(R.id.button1);
btn.setOnClickListener(this);
start = false;
new Thread(new Server()).start();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
}
new Thread(new Client()).start();
Handler = new Handler() {
@Override
public void handleMessage(Message msg) {
String text = (String) msg.obj;
text1.append(text);
}
};
}
this class Client
@SuppressLint("NewApi")
public class Client implements Runnable {
@Override
public void run() {
while (start == false) {
}
try {
Thread.sleep(500);
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
InetAddress serverAddr = InetAddress.getByName(SERVERIP);
updatetrack("Client: Start connecting\n");
DatagramSocket socket = new DatagramSocket();
byte[] buf;
if (!input.getText().toString().isEmpty()) {
buf = input.getText().toString().getBytes();
} else {
buf = ("Default message").getBytes();
}
DatagramPacket packet = new DatagramPacket(buf, buf.length,
serverAddr, SERVERPORT);
updatetrack("Client: Sending '" + new String(buf) + "'\n");
socket.send(packet);
updatetrack("Client: Message sent\n");
updatetrack("Client: Succeed!\n");
} catch (Exception e) {
updatetrack("Client: Error!\n");
}
}
}
this class Client
public class Server implements Runnable {
@Override
public void run() {
while (start = false) {
try {
InetAddress serverAddress = InetAddress.getByName(SERVERIP);
updatetrack("nServer: Start connectingn");
DatagramSocket socket = new DatagramSocket(SERVERPORT,
serverAddress);
byte[] buffer = new byte[17];
DatagramPacket packet = new DatagramPacket(buffer,
buffer.length);
updatetrack("Server: Receivingn");
socket.receive(packet);
updatetrack("Server: Message received:"
+ new String(packet.getData()) + "'n");
updatetrack("Server : Succed!n");
} catch (Exception e) {
updatetrack("Server: Error!n" + e.getMessage());
}
}
}
}
public void updatetrack(String s) {
Message msg = new Message();
String textTochange = s;
msg.obj = textTochange;
Handler.sendMessage(msg);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (v.getId() == R.id.button1)
start = true;
}
}
help me please ? why just once send message Thanks before