用于局域网通信的基于udp协议的工具类。具备发送关闭功能。
直接上代码：

package com.example.testapp;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.text.TextUtils;
import android.util.Log;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class UdpSocketUtils extends Thread {


    private static final int BROADCAST_PORT = 9526;
    private static final String TAG = "udp_socket_utils";
    private DatagramSocket socket;
    private OnUdpListener onUdpListener;
    private boolean isRunning = true;

    private final ExecutorService service = Executors.newSingleThreadExecutor();

    public void setOnUdpListener(OnUdpListener onUdpListener) {
        this.onUdpListener = onUdpListener;
    }

    public interface OnUdpListener {
        void onBuffer(byte[] bytes);

        void onRelease();
    }

    public void release() {
        Log.i(TAG, "release: enter is wait: socket:" + socket);
        if (socket == null || !isRunning) {
            Log.i(TAG, "release: again enter");
            return;
        }
        isRunning = false;

        if (onUdpListener != null) {
            onUdpListener.onRelease();
            onUdpListener = null;
        }

        // cancel task
        try {
            List<Runnable> pendingTask = service.shutdownNow();
            Log.i(TAG, "release: cancel count:" + pendingTask.size());
        } catch (Exception e) {
            Log.i(TAG, "release: error:" + e.getMessage());
        }

        // release socket
        if (socket != null) {
            try {
                socket.close();
            } catch (Exception e) {
                Log.e(TAG, "release: error:" + e.getMessage(), e);
            }
            socket = null;
        }

        Log.i(TAG, "release: finish");
    }

    public void sendInner(byte[] buf, String ip) {
        if (buf == null || buf.length < 4 || !isRunning) {
            Log.i(TAG, "sendInner: len less four");
            return;
        }

        service.execute(() -> {
            try {
                DatagramPacket sendPacket = new DatagramPacket(buf, buf.length);
                sendPacket.setAddress(InetAddress.getByName(ip));
                sendPacket.setPort(BROADCAST_PORT);
                socket.send(sendPacket);
            } catch (IOException e) {
                e.printStackTrace();
                Log.i(TAG, "sendInner: error:" + e.getMessage());
            }
        });
    }

    public void waitSelf() {
        try {
            join();
        } catch (Exception e) {
            Log.i(TAG, "waitSelf: error:" + e.getMessage());
        }
        Log.i(TAG, "waitSelf: is all end");
    }

    @Override
    public void run() {
        super.run();
        int bufferMaxSize = 4096;
        byte[] by = new byte[bufferMaxSize];
        try {
            socket = new DatagramSocket(BROADCAST_PORT);
            socket.setBroadcast(true);

            while (isRunning) {
                try {
                    // receive data
                    DatagramPacket receivePacket = new DatagramPacket(by, by.length);
                    // Join thread
                    socket.receive(receivePacket);

                    // receive package
                    byte[] buffer = new byte[receivePacket.getLength()];
                    System.arraycopy(receivePacket.getData(), 0, buffer, 0, buffer.length);
                    String ip = receivePacket.getAddress().getHostAddress();

                    receiveData(buffer);
                    Log.i(TAG, "run: other ip:" + ip + "; data len:" + buffer.length);
                } catch (Exception e) {
                    e.printStackTrace();
                    Log.i(TAG, "run: error:" + e.getMessage());
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            Log.i(TAG, "run: error:" + e.getMessage());
        }

        release();

    }

    private void receiveData(byte[] buffer) {
        if (onUdpListener != null && isRunning) {
            onUdpListener.onBuffer(buffer);
        }
    }

    public void sendBroadCast(Context context, String msg) {
        String ipAddress = getIPAddress(context);
        Log.i(TAG, "sendBroadCast: ip origin:" + ipAddress);
        if (TextUtils.isEmpty(ipAddress) || ipAddress.length() < 8) {
            return;
        }
        try {
            int index = ipAddress.lastIndexOf(".");
            ipAddress = ipAddress.substring(0, index) + ".255";
            Log.i(TAG, "sendBroadCast: send ip:" + ipAddress);
            sendInner(msg.getBytes(), ipAddress);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    // ------------------------------------------------ tools begin

    public String getIPAddress(Context context) {
        String ipAddress = null;
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        Network network = connectivityManager.getActiveNetwork();
        NetworkCapabilities networkCapabilities = connectivityManager.getNetworkCapabilities(network);
        if (networkCapabilities != null && networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
            ipAddress = getIPAddressFromWifiManager(context);
        }

        return ipAddress;
    }

    private String getIPAddressFromWifiManager(Context context) {
        WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        WifiInfo wifiInfo = wifiManager.getConnectionInfo();
        int ipAddress = wifiInfo.getIpAddress();
        return formatIpAddress(ipAddress);
    }

    public static String formatIpAddress(int ip) {
        try {
            // 将整数形式的 IP 地址转换为字节数组
            byte[] bytes = ByteBuffer.allocate(4).putInt(ip).array();

            // 由于 InetAddress.getByAddress() 需要网络字节顺序（big-endian），我们需要反转字节数组
            for (int i = 0; i < bytes.length / 2; i++) {
                byte temp = bytes[i];
                bytes[i] = bytes[bytes.length - i - 1];
                bytes[bytes.length - i - 1] = temp;
            }

            // 获取 InetAddress 对象并返回字符串形式的 IP 地址
            InetAddress inetAddress = InetAddress.getByAddress(bytes);
            return inetAddress.getHostAddress();
        } catch (Exception e) {
            // UnknownHostException 是一个检查异常，你可以选择记录或者处理这个异常
            e.printStackTrace();
            return null;
        }
    }

}