Android MulticastSocket IP组播

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();
    }

}