1. 创建一个DatagramSocket对象，并指定监听的端口号
DatagramSocket socket = new DatagramSocket (4567);
2. 创建一个byte数组用于接收
byte data[] = new byte[1024];
3. 创建一个空的DatagramPackage对象
DatagramPackage package = new DatagramPackage(data , data.length);
4. 使用receive方法接收发送方所发送的数据,同时这也是一个阻塞的方法
socket.receive(package);
5. 得到发送过来的数据
new String(package.getData() , package.getOffset() , package.getLength());
发送方创建步骤：
1. 创建一个DatagramSocket对象
DatagramSocket socket = new DatagramSocket (4567);
2. 创建一个 InetAddress ， 相当于是地址
InetAddress serverAddress = InetAddress.getByName("想要发送到的那个IP地址");
3. 这是随意发送一个数据
String str = "hello";
4. 转为byte类型
byte data[] = str.getBytes();
5. 创建一个DatagramPacket 对象，并指定要讲这个数据包发送到网络当中的哪个地址，以及端口号
DatagramPacket package = new DatagramPacket (data , data.length , serverAddress , 4567);
6. 调用DatagramSocket对象的send方法 发送数据
socket . send(package);
http://www.cnblogs.com/lee0oo0/archive/2012/04/04/2431907.html1、可先在oncreate()方法里面实例化一个WifiManager.MulticastLock 对象lock；具体如下：
WifiManager manager = (WifiManager) this .getSystemService(Context.WIFI_SERVICE); WifiManager.MulticastLock lock= manager.createMulticastLock("test wifi");2、在调用广播发送、接收报文之前先调用lock.acquire()方法；
3、用完之后及时调用lock.release()释放资源，否决多次调用lock.acquire()方法，程序可能会崩，详情请见
Caused by: java.lang.UnsupportedOperationException: Exceeded maximum number of wifi locks
注；记得在配置文件里面添加如下权限：
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />经过这样处理后，多数手机都能正常发送接收到广播报文。
本小点转载自Android手机接收不到UDP报文
在UDP通信中，android端发送UDP广播包没有问题。至于接收的话，有时候不能接收到包。但是如果UDP包中指定了目标主机的地址的话，那么android端就能正常接收。
下面上一段代码，大家可用这段代码进行测试。
1、在一个Service里面，我们创建一个线程
public void onCreate() {//用于创建线程 WifiManager manager = (WifiManager) this .getSystemService(Context.WIFI_SERVICE); udphelper = new UdpHelper(manager); //传递WifiManager对象，以便在UDPHelper类里面使用MulticastLock udphelper.addObserver(MsgReceiveService.this); tReceived = new Thread(udphelper); tReceived.start(); super.onCreate(); }2、弄一个UDP帮助类，这个类主要用于发送和接收数据
package com.example.com.ihome.bang.util; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.net.MulticastSocket; import java.net.SocketException; import java.net.UnknownHostException; import java.util.Observable; import com.example.com.ihome.bang.tool.SendThread; import android.net.wifi.WifiManager; import android.util.Log; /** * * UdpHelper帮助类 * * @author 陈喆榕 * */ public class UdpHelper implements Runnable { public Boolean IsThreadDisable = false;//指示监听线程是否终止 private static WifiManager.MulticastLock lock; InetAddress mInetAddress; public UdpHelper(WifiManager manager) { this.lock= manager.createMulticastLock("UDPwifi"); } public void StartListen() { // UDP服务器监听的端口 Integer port = 8903; // 接收的字节大小，客户端发送的数据不能超过这个大小 byte[] message = new byte[100]; try { // 建立Socket连接 DatagramSocket datagramSocket = new DatagramSocket(port); datagramSocket.setBroadcast(true); DatagramPacket datagramPacket = new DatagramPacket(message, message.length); try { while (!IsThreadDisable) { // 准备接收数据 Log.d("UDP Demo", "准备接受"); this.lock.acquire(); datagramSocket.receive(datagramPacket); String strMsg=new String(datagramPacket.getData()).trim(); Log.d("UDP Demo", datagramPacket.getAddress() .getHostAddress().toString() + ":" +strMsg );this.lock.release(); } } catch (IOException e) {//IOException e.printStackTrace(); } } catch (SocketException e) { e.printStackTrace(); } } public static void send(String message) { message = (message == null ? "Hello IdeasAndroid!" : message); int server_port = 8904; Log.d("UDP Demo", "UDP发送数据:"+message); DatagramSocket s = null; try { s = new DatagramSocket(); } catch (SocketException e) { e.printStackTrace(); } InetAddress local = null; try { local = InetAddress.getByName("255.255.255.255"); } catch (UnknownHostException e) { e.printStackTrace(); } int msg_length = message.length(); byte[] messageByte = message.getBytes(); DatagramPacket p = new DatagramPacket(messageByte, msg_length, local, server_port); try { s.send(p); s.close(); } catch (IOException e) { e.printStackTrace(); } } @Override public void run() { StartListen(); } }作者：kissazi2 出处：http://www.cnblogs.com/kissazi2/ 本文版权归作者所有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
最后， 添加个人的实例 ： package com.example.android.helloactivity; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import com.example.andriod.udp.UDPClient; import com.example.andriod.udp.UDPServer; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class MainAct extends Activity { EditText msg_et = null; Button send_bt = null; TextView info_tv = null; private static final String TAG ="MainAct"; private UDPClient client; private String sendInfo; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.udp_test); msg_et = (EditText) findViewById(R.id.edit_msg); send_bt = (Button) findViewById(R.id.send_bt); info_tv = (TextView) findViewById(R.id.receive_msg); info_tv.setText("source"); // 开启服务器 ExecutorService exec = Executors.newCachedThreadPool(); UDPServer server = new UDPServer(); exec.execute(server); // 发送消息 send_bt.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { myThread1 thread = new myThread1("22"); new Thread(thread).start(); } }); } final Handler mHander = new Handler() { public void handleMessage(Message msg) { // TODO Auto-generated method stub //super.handleMessage(msg); info_tv.setText(sendInfo); Log.d(TAG, "client.send()="); } }; class myThread1 implements Runnable { private String threadName; public myThread1(String name) { this.threadName = name; } public void run() { Log.d(TAG, "MyThread execu"+msg_et.getText().toString()); client = new UDPClient(msg_et.getText().toString()); sendInfo=client.send(); Message msg = mHander.obtainMessage(); msg.arg1=1; mHander.sendMessage(msg); Log.d(TAG, "client.send()="); } } } package com.example.andriod.udp; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.SocketException; import android.util.Log; public class UDPServer implements Runnable { private static final int PORT = 6000; private byte[] msg = new byte[2048]; private boolean life = true; public UDPServer() { } public boolean isLife() { return life; } public void setLife(boolean life) { this.life = life; } @Override public void run() { DatagramSocket dSocket = null; DatagramPacket dPacket = new DatagramPacket(msg, msg.length); try { dSocket = new DatagramSocket(PORT); while (life) { try { dSocket.receive(dPacket); Log.d("tian msg sever received", new String(dPacket.getData(), dPacket.getOffset(), dPacket.getLength()) + "dPacket.getLength()=" + dPacket.getLength()); } catch (IOException e) { e.printStackTrace(); } } } catch (SocketException e) { e.printStackTrace(); } } } package com.example.andriod.udp; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.net.SocketException; import java.net.UnknownHostException; import android.util.Log; public class UDPClient { private static final int SERVER_PORT = 6000; private DatagramSocket dSocket = null; private String msg; public UDPClient(String msg) { super(); this.msg = msg; } public String send() { StringBuilder sb = new StringBuilder(); InetAddress local = null; try { local = InetAddress.getByName("localhost"); // 本机测试 sb.append("已找到服务器,连接中...").append("/n"); } catch (UnknownHostException e) { sb.append("未找到服务器.").append("/n"); e.printStackTrace(); } try { dSocket = new DatagramSocket(); // 注意此处要先在配置文件里设置权限,否则会抛权限不足的异常 sb.append("正在连接服务器...").append("/n"); } catch (SocketException e) { e.printStackTrace(); sb.append("服务器连接失败.").append("/n"); } int msg_len = msg == null ? 0 : msg.length(); DatagramPacket dPacket = new DatagramPacket(msg.getBytes(), msg_len, local, SERVER_PORT); try { dSocket.send(dPacket); Log.d("tian", "msg=="+msg+"dpackage="+dPacket.getData()+"dPacket.leng="+dPacket.getLength()); sb.append("消息发送成功!").append("/n"); } catch (IOException e) { e.printStackTrace(); sb.append("消息发送失败.").append("/n"); } dSocket.close(); return sb.toString(); } }