android ONVIF 组播探测在线摄像机

http://blog.csdn.net/ghostyu/article/details/8182516

Android的Wifi，默认情况下是不接受组播的，见：http://developer.android.com/reference/android/net/wifi/WifiManager.MulticastLock.html

默认情况下，应用是不接收组播信息的，这样要接收处理的报文太多，很快就会把电池用尽。要知道移动设备（特指电话一类的，平板要好得多）目前最重要的因素是电量。

要想打开组播功能，有以下几个步骤：

• 在Manifest文件中加入：android.permission.CHANGE_WIFI_MULTICAST_STATE，这个权限
• 获取到MulticastLock对象，这个对象不能直接实例化，要通过WifiManager间接得到，工厂模式
• 调用MulticastLock对象的acquire方法，获取到组播锁
• 相应的，用完组播，为了不浪费电力，要调用MulticastLock的release方法释放锁

1、创建组播用的udp socket，

2、绑定组播地址为239.255.255.250，端口为3702，因为ws-discovery的组播地址和端口就是为239.255.255.250和3702

直接上代码：

public class MulticastDemoActivity extends Activity {   

    MulticastLock multicastLock;   

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);   

        allowMulticast();   

        try {
            NetUtil.findServerIpAddress();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }   

        Log.d("multicast.demo", "find ip ok.");   

        multicastLock.release();
    }   

    private void allowMulticast(){
        WifiManager wifiManager=(WifiManager)getSystemService(Context.WIFI_SERVICE);
        multicastLock=wifiManager.createMulticastLock("multicast.test");
        multicastLock.acquire();
    }
}

public class NetUtil {   

    private static final String TAG="Net.Utils";
    private static final int MULTICAST_PORT=5111;
    private static final String GROUP_IP="224.5.0.7";
    private static byte[] sendData;   

    static{
        sendData=new byte[4];
        // 0xEE78F1FB
        sendData[3] = (byte) 0xEE;
        sendData[2] = (byte) 0×78;
        sendData[1] = (byte) 0xF1;
        sendData[0] = (byte) 0xFB;
    }   

    public static String findServerIpAddress() throws IOException{
        String ip=null;  

        MulticastSocket multicastSocket=new MulticastSocket(MULTICAST_PORT);
        multicastSocket.setLoopbackMode(true);
        InetAddress group = InetAddress.getByName(GROUP_IP);
        multicastSocket.joinGroup(group);   

        DatagramPacket packet=new DatagramPacket(sendData, sendData.length,group,MULTICAST_PORT);   

        for(;;){
            multicastSocket.send(packet);
            Log.d(TAG,">>>send packet ok");   

            byte[] receiveData=new byte[256];
            packet=new DatagramPacket(receiveData, receiveData.length);
            multicastSocket.receive(packet);   

            String packetIpAddress=packet.getAddress().toString();
            packetIpAddress=packetIpAddress.substring(1, packetIpAddress.length());
            Log.d(TAG,"packet ip address: "+packetIpAddress);   

            StringBuilder packetContent=new StringBuilder();
            for(int i=0;i<receiveData.length;i++){
                if(receiveData[i]==0){
                    break;
                }
                packetContent.append((char)receiveData[i]);
            }
            ip=packetContent.toString();
            Log.d(TAG,"packet content ip is: "+ip);   

            if(ip.equals(packetIpAddress)){
                Log.d(TAG,"find server ip address: "+ip);
                break;
            }else{
                Log.d(TAG,"not find server ip address, continue …");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                }
            }
        }   

        return ip;
    }
}  

上面代码供参考，但是没有测试在htc手机上成功

下面是本人修改过的代码：

public static String findServerIpAddress() throws IOException {

        String sinfo = "";
        byte[] sendData = sinfo.getBytes();
        String ip = "";
        try {
            MulticastSocket multicastSocket = new MulticastSocket(
                    MULTICAST_PORT);
            multicastSocket.setLoopbackMode(true);//修改添加代码部分不添加不能发送成功
            InetAddress group = InetAddress.getByName(GROUP_IP);
            multicastSocket.setLoopbackMode(true);
            multicastSocket.joinGroup(group);
            multicastSocket.setSoTimeout(10000);
            DatagramPacket packet = new DatagramPacket(sendData,
                    sendData.length, group, MULTICAST_PORT);
            for (;;) {
                multicastSocket.send(packet);
                Log.d(TAG, ">>>send packet ok");
                byte[] receiveData = new byte[256];
                packet = new DatagramPacket(receiveData, receiveData.length);
                multicastSocket.receive(packet);
                String packetIpAddress = packet.getAddress().toString();
                packetIpAddress = packetIpAddress.substring(1,
                        packetIpAddress.length());
                Log.d(TAG, "packet ip address: " + packetIpAddress);
                StringBuilder packetContent = new StringBuilder();
                for (int i = 0; i < receiveData.length; i++) {
                    if (receiveData[i] == 0) {
                        break;
                    }
                    packetContent.append((char) receiveData[i]);
                }
                ip = packetContent.toString();
                Log.d(TAG, "packet content ip is: " + ip);
                if (ip.equals(packetIpAddress)) {
                    Log.d(TAG, "find server ip address: " + ip);
                    break;
                } else {
                    Log.d(TAG, "not find server ip address, continue …");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                    }
                }
            }
        } catch (Exception ee) {
            Log.d(TAG, ee.toString());
        }
        return ip;
    }

http://blog.csdn.net/lvron/article/details/6606755