Android IP多点组播MulticastSocket

MulticastSocket是对等的关系，也就是他们通过IP多点组播保留的地址来相互接收在这个组的Socket发送的消息

我写了一个例子，MultiSocketB是一个service,用于先接收再发送，MultiSocketA用于先发送再接收，完成这一动作后退出

记得要加使用网络的权限

<uses-permission android:name="android.permission.INTERNET" />

先看MultiSocketA

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.multicastsocketsend"
    android:versionCode="1"
    android:versionName="1.0" >
	<uses-permission android:name="android.permission.INTERNET" />
	
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.multicastsocketsend.MultiSocketA"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

package com.example.multicastsocketsend;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.util.Log;

/**
 * @author lijinwei
 * 本应用用于实现IP多点广播
 * 若要使用多点广播时，则需要让一个数据报标有一组目标主机地址，当数据报发出后，整个组的所有主机都能收到该数据报。
 * IP多点广播（或多点发送）实现了将单一信息发送到多个接收者的广播，其思想是设置一组特殊网络地址作为多点广播地址，每一个多点广播地址都被看做一个组，
 * 当客户端需要发送、接收广播信息时，加入到该组即可。
 */
public class MultiSocketA extends Activity {
	protected static final String TAG = "MultiSocketA";
	private Handler mHandler;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		//通过Handler启动线程  
        HandlerThread handlerThread = new HandlerThread("MultiSocketA");
        handlerThread.start();
        mHandler =  new Handler(handlerThread.getLooper());
        mHandler.post(mRunnable);  
	}

	private Runnable mRunnable = new Runnable() {  
        
        public void run() {
        	Log.v(TAG, "run...");
        	try {
        		sendMultiBroadcast();
			} catch (Exception e) {
				e.printStackTrace();
			}
        }

		private void sendMultiBroadcast() throws IOException {
			Log.v(TAG, "sendMultiBroadcast...");
			/*
			 * 实现多点广播时，MulticastSocket类是实现这一功能的关键，当MulticastSocket把一个DatagramPacket发送到多点广播IP地址，
			 * 该数据报将被自动广播到加入该地址的所有MulticastSocket。MulticastSocket类既可以将数据报发送到多点广播地址，
			 * 也可以接收其他主机的广播信息
			 */
			MulticastSocket socket = new MulticastSocket(8600);
			//IP协议为多点广播提供了这批特殊的IP地址，这些IP地址的范围是224.0.0.0至239.255.255.255
			InetAddress address = InetAddress.getByName("224.0.0.1");
			/*
			 * 创建一个MulticastSocket对象后，还需要将该MulticastSocket加入到指定的多点广播地址，
			 * MulticastSocket使用jionGroup()方法来加入指定组；使用leaveGroup()方法脱离一个组。
			 */
			socket.joinGroup(address);
			
			/*
			 * 在某些系统中，可能有多个网络接口。这可能会对多点广播带来问题，这时候程序需要在一个指定的网络接口上监听，
			 * 通过调用setInterface可选择MulticastSocket所使用的网络接口；
			 * 也可以使用getInterface方法查询MulticastSocket监听的网络接口。
			 */
			//socket.setInterface(address);
			
			DatagramPacket packet;
			//发送数据包
			Log.v(TAG, "send packet");
			byte[] buf = "Hello I am MultiSocketA".getBytes();
			packet = new DatagramPacket(buf, buf.length, address, 8601);
			socket.send(packet);
			
			//接收数据
			Log.v(TAG, "receiver packet");
			byte[] rev = new byte[512];
			packet = new DatagramPacket(rev, rev.length);
			socket.receive(packet);
			Log.v(TAG, "get data = " + new String(packet.getData()).trim());	//不加trim，则会打印出512个byte，后面是乱码
			
			//退出组播
			socket.leaveGroup(address);
			socket.close();
		}  
          
    };  
}

再看MultiSocketB

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.multicastsocketreceiver"
    android:versionCode="1"
    android:versionName="1.0" >
	<uses-permission android:name="android.permission.INTERNET" />

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.multicastsocketreceiver.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <service android:name=".MultiSocketB" />
        
    </application>

</manifest>

package com.example.multicastsocketreceiver;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		Intent intent = new Intent();
		intent.setClass(this, MultiSocketB.class);
		this.startService(intent);
	}

}

package com.example.multicastsocketreceiver;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.util.Log;

public class MultiSocketB extends Service {
	protected static final String TAG = "MultiSocketB";
	private Handler mHandler;

	@Override
	public IBinder onBind(Intent intent) {
		return null;
	}

	@Override
	public void onCreate() {
		super.onCreate();
		Log.v(TAG, "onCreate");
		// 通过Handler启动线程
		HandlerThread handlerThread = new HandlerThread("MultiSocketB");
		handlerThread.start();
		mHandler = new Handler(handlerThread.getLooper());
		mHandler.post(mRunnable);
	}

	private Runnable mRunnable = new Runnable() {
		public void run() {
			Log.v(TAG, "run...");
			try {
				receiveMultiBroadcast();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

	};

	protected void receiveMultiBroadcast() throws IOException {
		Log.v(TAG, "receiveMultiBroadcast...");
		MulticastSocket socket = new MulticastSocket(8601);
		InetAddress address = InetAddress.getByName("224.0.0.1");
		socket.joinGroup(address);

		DatagramPacket packet;

		// 接收数据
		Log.v(TAG, "receiver packet");
		byte[] rev = new byte[512];
		packet = new DatagramPacket(rev, rev.length);
		socket.receive(packet);
		String receiver = new String(packet.getData()).trim();	//不加trim，则会打印出512个byte，后面是乱码
		Log.v(TAG, "get data = " + receiver);

		//发送数据包
		Log.v(TAG, "send packet");
		String process_receiver = "I am MultiSocketB, I got " + receiver;
		byte[] buf = process_receiver.getBytes();
		packet = new DatagramPacket(buf, buf.length, address, 8600);
		socket.send(packet);
		
		//退出组播
		socket.leaveGroup(address);
		socket.close();
	}

}