MDT5_1_Ueberwachungssystem_G1/app/src/main/java/com/example/ueberwachungssystem/WifiCommunication.java

package com.example.ueberwachungssystem;
import android.annotation.SuppressLint;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Enumeration;

public class WifiCommunication {
    private final MainActivity mainActivity;
    private final InetAddress address;
    private final int port;

    private String messageToSend;
    volatile private boolean send;
    private final DatagramSocket socket;
    volatile private boolean running;
    @SuppressLint("SetTextI18n")
    public WifiCommunication(MainActivity mainActivity, int port) {
        this.mainActivity = mainActivity;
        this.port = port;
        try {
            socket = new DatagramSocket(this.port);
            socket.setBroadcast(true);
            address = InetAddress.getByName("255.255.255.255");
            running = true;
            send = false;
            new ReceiveThread().start();
            new SendThread().start();
        } catch (SocketException | UnknownHostException e) {
            throw new RuntimeException(e);
        }
        mainActivity.runOnUiThread(() -> mainActivity.tvMessages.setText("Communication running"));
    }
    private class ReceiveThread extends Thread {
        private StringBuffer rxStringBuffer = new StringBuffer();
        private String rxString;
        private String previousRxString = "";
        @Override
        public void run() {
            try {
                do {
                    byte[] rxBuffer = new byte[512];
                    InetAddress fromAdress;
                    int fromPort;
                    DatagramPacket rxPacket = new DatagramPacket(rxBuffer, rxBuffer.length);
                    socket.receive(rxPacket);
                    fromAdress = rxPacket.getAddress();
                    fromPort = rxPacket.getPort();
                    rxString = new String(rxBuffer, 0, rxPacket.getLength());
                    if(!previousRxString.equals(rxString)) {
                        mainActivity.runOnUiThread(() -> mainActivity.tvMessages.setText(rxStringBuffer));
                        rxStringBuffer.append("Adress: " + fromAdress).append(" Port: " + fromPort).append(" Message " +rxString).append("\n");
                    }
                    previousRxString = rxString;

                } while (running);
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    private class SendThread extends Thread {
        private int tmpCnt = 0;
        @Override
        public void run() {
            try {
                do {
                    if(send)
                    {
                        send = false;

                        String txString = getLocalIpAddress() + " sends:" +messageToSend+ " Count: " + tmpCnt++;
                        byte[] txBuffer = txString.getBytes();

                        DatagramPacket txPacket = new DatagramPacket(txBuffer, txBuffer.length, address, port);

                        for(int i = 0; i < 20; i++) {
                            socket.send(txPacket);
                        }
                    }
                } while (running);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    public static String getLocalIpAddress() {
        try {
            for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
                NetworkInterface networkInterface = (NetworkInterface) ((Enumeration<?>) en).nextElement();
                for (Enumeration<InetAddress> addresses = networkInterface.getInetAddresses(); addresses.hasMoreElements();) {
                    InetAddress inetAddress = addresses.nextElement();
                    if (!inetAddress.isLoopbackAddress() && inetAddress instanceof Inet4Address) {
                        return inetAddress.getHostAddress();
                    }
                }
            }
        } catch (SocketException ex) {
            ex.printStackTrace();
        }
        return null;
    }

    public void sendTrue(String message){
        send = true;
        messageToSend = message;
    }
    public void stopCommunication() {
        running = false;
        socket.close();
    }
}