android java udp广播用于局域网搜索扫描设备。

组播通过把224.0.0.0-239.255.255.255的D类地址作为目的地址，有一台源主机发出目的地址是以上范围组播地址的报文，在网络中，如果有其他主机对于这个组的报文有兴趣的，可以申请加入这个组，并可以接受这个组，而其他不是这个组的成员是无法接受到这个组的报文的。UDP编程常常使用，但是广播和多播倒很少用到，依据协议的样子，在局域网内该有很大的作为。组播是一种数据包传输方式，当有多台主机同

代码s贝多芬的音符

1424人浏览 · 2022-12-30 14:55:04

代码s贝多芬的音符 · 2022-12-30 14:55:04 发布

        DatagramSocket socket = new DatagramSocket();
            //设置接收等待时长
            socket.setSoTimeout(LanCommConfig.RECEIVE_TIME_OUT);
            byte[] sendData = new byte[1024];
            //使用广播形式（目标地址设为255.255.255.255）的udp数据包
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, InetAddress.getByName("255.255.255.255"), Const.DEVICE_BROADCAST_PORT);
            byte[] hostAddress = Utils.getLocalIPAddress();
            byte[]  b="啦啦啦啦啦啦啦啦啦噢噢噢噢噢噢噢噢".getBytes();
            byte[] broadcastData = packBroadcastData(hostAddress, b);
            sendPacket.setData(broadcastData);
            //发送udp数据包
            socket.send(sendPacket);
            Log.v(TAG, Utils.getDeviceIp() + Const.SEND_SYMBOL + "局域网广播 成功");


    /**
     * 协议规范
     * #(1) + packageType(1) +  ip(4) + dataLength(4) + [data]
     *
     * @param bytes
     * @param hostAddress
     * @return
     */
        private int type = Const.PACKET_TYPE_BROADCAST;
    private byte[] packBroadcastData(byte[] hostAddress, byte[] bytes) {
        //        Trace.d(TAG, "packBroadcastData() ：" + Arrays.toString(hostAddress));
        //        Trace.d(TAG, "packBroadcastData() : " + Arrays.toString(bytes));
        byte[] lengthBytes = ConvertUtils.intToByteArray(bytes.length);
        byte[] data = new byte[2 + hostAddress.length + bytes.length + lengthBytes.length];
        data[0] = Const.PACKET_PREFIX;
        data[1] = (byte) type;
        //        Trace.d(TAG, "packBroadcastData() : " + Arrays.toString(lengthBytes));
        System.arraycopy(hostAddress, 0, data, 2, hostAddress.length);
        System.arraycopy(lengthBytes, 0, data, 2 + hostAddress.length, lengthBytes.length);
        if (bytes != null && bytes.length != 0) {
            System.arraycopy(bytes, 0, data, 2 + hostAddress.length + lengthBytes.length, bytes.length);
        }
        Log.v(TAG, Utils.getDeviceIp() + Const.SEND_SYMBOL + "局域网广播 package data:\r\n" + Arrays.toString(data));
        return data;
    }

把自身的ip地址发送过去。

package com.fighter.lancomm.utils;

import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Enumeration;

/**
 * @author sts
 * @date 2020/1/15
 */
public class Utils {

    /**
     * 获取内网IP地址
     *
     * @return
     * @throws SocketException
     */
    public static byte[] getLocalIPAddress() throws SocketException {
        for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {
            NetworkInterface intf = en.nextElement();
            for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {
                InetAddress inetAddress = enumIpAddr.nextElement();
                if (!inetAddress.isLoopbackAddress() && (inetAddress instanceof Inet4Address)) {
                    return inetAddress.getAddress();
                }
            }
        }
        return new byte[4];
    }

    public static String ipbyteToString(byte[] ip) throws UnknownHostException {
        return InetAddress.getByAddress(ip).getHostAddress();
    }

    public static String getDeviceIp() {
        try {
            byte[] localIPAddress = getLocalIPAddress();
            return Utils.ipbyteToString(localIPAddress);
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        return "";
    }
}