public class DatagramUtil
{
 public static final int BOADCAST_PORT = 8888;
 public static final String DEST_IP = "192.168.1.101";
 private static final int DATA_LEN = 50000;
 //定義本程序私聊的Socket實例
 private DatagramSocket singleSocket = null;
 //定義接收網(wǎng)絡(luò)數(shù)據(jù)的字符數(shù)組
 byte[] inBuff = new byte[DATA_LEN];
 private Handler handler;

 //構(gòu)造器，初始化資源
 public DatagramUtil(Handler handler) throws Exception
 {
  this.handler = handler;
  //創(chuàng)建用于私聊的DatagramSocket對象
  singleSocket = new DatagramSocket();
  new ReadSingle().start();
 }

 //定義單獨用戶發(fā)送消息的方法
 public void sendSingle(byte[] msg)
 {
  try
  {
   DatagramPacket packet = new DatagramPacket(new byte[0] , 0 , InetAddress.getByName(DEST_IP) , BOADCAST_PORT);
   packet.setData(msg);
   singleSocket.send(packet);
  }
  catch (IOException e)
  {
   e.printStackTrace();
  }
 }

 //不斷地從DatagramSocket中讀取數(shù)據(jù)的線程
 class ReadSingle extends Thread
 {
  byte[] singleBuff = new byte[DATA_LEN];
  private DatagramPacket singlePacket = new DatagramPacket(singleBuff , singleBuff.length);

  @Override
  public void run()
  {
   while (true)
   {
    // 讀取Socket中的數(shù)據(jù)
    try
    {
     //讀取Socket中的數(shù)據(jù)
     singleSocket.receive(singlePacket);
     //處理得到的消息
     Message msg = new Message();
     msg.what = 0x123;
     msg.obj = singleBuff;
     handler.sendMessage(msg);
    }
    catch (IOException e)
    {
     e.printStackTrace();
     if (singleSocket != null)
     {
      //關(guān)閉該Socket對象
      singleSocket.close();
     }
    }
   }
  }
 }
}

public class MainActivity extends Activity
{
 private Button button;
 private ImageView img;
 private DatagramUtil datagramUtil;
 Handler handler = new Handler()
 {
  @Override
  public void handleMessage(Message msg)
  {
   if (msg.what == 0x123)
   {
    byte[] result = (byte[]) msg.obj;
    img.setImageBitmap(BitmapFactory.decodeByteArray(result , 0 , result.length));
   }
  }
 };

 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main_activity);
  button = (Button) findViewById(R.id.send_img_all);
  img = (ImageView) findViewById(R.id.receiver_img);

  try
  {
   datagramUtil = new DatagramUtil(handler);
   sendData(stringYoByte());
  }
  catch (Exception e)
  {
   e.printStackTrace();
  }

  button.setOnClickListener(new View.OnClickListener()
  {
   @Override
   public void onClick(View view)
   {
    sendData(bitMapToByte());
   }
  });
 }

 private void sendData(final byte[] msg)
 {
  new Thread()
  {
   @Override
   public void run()
   {
    datagramUtil.sendSingle(msg);
   }
  }.start();
 }

 public byte[] bitMapToByte()
 {
  Bitmap bitmap = BitmapFactory.decodeResource(getResources() , R.drawable.wenqing);
  ByteArrayOutputStream byteArray = new ByteArrayOutputStream();
  bitmap.compress(Bitmap.CompressFormat.PNG , 100 , byteArray);
  bitmap.recycle();
  return byteArray.toByteArray();
 }

 public byte[] stringYoByte()
 {
  String loginStr = "hello";
  return loginStr.getBytes();
 }
}

public class UDPServer
{
 public static final int PORT = 8888;
 private static final int DATA_LEN = 50000;
 byte[] inBuff = new byte[DATA_LEN];
 private DatagramPacket inPacket = new DatagramPacket(inBuff , inBuff.length);
 private DatagramPacket outPacket;
 private DatagramSocket serverSocket;
 private Set<SocketAddress> socketAddressList = Collections.synchronizedSet(new HashSet<SocketAddress>());

 public void init() throws IOException
 {
  serverSocket = new DatagramSocket(PORT);
  while (true)
  {
   serverSocket.receive(inPacket);
   String result = new String(inBuff , 0 , inBuff.length);
   if (result.trim().equals("hello"))
   {
    socketAddressList.add(inPacket.getSocketAddress());
   }
   else
   {
    for (Iterator<SocketAddress> iterator = socketAddressList.iterator(); iterator.hasNext() ; )
    {
     SocketAddress socketAddress = iterator.next();
     outPacket = new DatagramPacket(inBuff , inBuff.length , socketAddress);
     serverSocket.send(outPacket);
    }
   }
  }
 }

 public static void main(String[] args) throws IOException
 {
  new UDPServer().init();
 }
}