Android Studio(Java) Client unable to connect on Android Server

Question

I have just started learning TCPSocket recently. I hope to write a quiz app online through a socket using Android Studio. However, during the execution of the client, it was unable to connect to the server. I repeatedly checked a lot of data and code, but couldn't find a solution

This is the Server part code I currently have:

public class ServerWaitStart extends AppCompatActivity {
    private static GlobalVariable gv;

    private ServerSocket serverSocket;

    TextView currentNum;
    private int count = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_11_server_wait_start);

        gv = (GlobalVariable)getApplicationContext();

        TextView IPaddress = findViewById(R.id.IPaddress);
        gv.IP = getLocalIP(this);
        IPaddress.setText("群組代碼:" + gv.IP);

        currentNum = findViewById(R.id.currentNum);
        serverConnect();
    }

    private ServerThread serverThread;

    public void serverConnect(){
        try {
            serverSocket= new ServerSocket(5050);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        serverThread = new ServerThread();
        serverThread.startServer();
    }

    class ServerThread extends Thread implements Runnable{

        private boolean serverRunning;
        private int count = 1;

        public void startServer(){
            serverRunning = true;
            start();
            System.out.println("startServer execute");
        }


        @Override
        public void run() {
            try {
                while(serverRunning){
                    System.out.println("in run");
                    Socket socket = serverSocket.accept();
                    System.out.println("accept!");
                    count++;

                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
                                dos.writeUTF(count + "\n");
                                // 立即發送
                                dos.flush();
                                currentNum.setText("目前已加入人數" + count);
                            } catch (IOException e) {
                                throw new RuntimeException(e);
                            }
                        }
                    });
                    if (gv.chooseNum == count){
                        break;
                    }
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }//ServerThread

This is the Client part code I currently have:

public class ClientWaitStart extends AppCompatActivity {
    private GlobalVariable gv;
    private TextView currentNum;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_07_client_wait_start);

        currentNum = findViewById(R.id.currentNum);
        gv = (GlobalVariable)getApplicationContext();
    }

    private Runnable Connection=new Runnable() {
        @Override
        public void run() {
            try {
                Socket socket = new Socket("10.0.2.16", 5050);
                System.out.println("client connected");

                DataInputStream dis = new DataInputStream(socket.getInputStream());
                String waitPeopleNum = dis.readUTF();

                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        currentNum.setText("目前已加入人數；" + waitPeopleNum);
                    }
                });

            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    };

Please help and ask me any questions that I left vague. Thank you, Laimo.

Server System.out 2023-06-02 13:22:19.504 5063-5063 System.out com.appcompat.app.quiz I startServer execute 2023-06-02 13:22:19.505 5063-5315 System.out com.appcompat.app.quiz I in run