public class NewConnection extends Thread {
Socket s;
int num;

NewConnection(int num, Socket s) {
    this.num = num;
    this.s = s;

    setDaemon(true);
    setPriority(NORM_PRIORITY);
    start();
    System.out.println("Got client");
}

public void run() {
    try {
        InputStream sin = s.getInputStream();
        OutputStream sout = s.getOutputStream();

        // Конвертируем потоки в другой тип, чтоб легче обрабатывать текстовые сообщения.
        DataInputStream in = new DataInputStream(sin);
        DataOutputStream out = new DataOutputStream(sout);

        String url = null;
        while (true) {
            url = "jdbc:mysql://localhost:3306/Clients"; // ожидаем пока клиент пришлет строку текста.
            System.out.println("sending url");
            out.flush(); // заставляем поток закончить передачу данных.
            System.out.println("Waiting for the next line...");
            System.out.println();
        }
    }catch (Exception x)
    {
        x.printStackTrace();
    }
}

connect.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            thread = new Thread(new Runnable() {
                public void run() {
                    int serverPort = 6666;
                    String address = "127.0.0.1";
                    try {
                        InetAddress ipAddress = InetAddress.getByName(address);
                        socket = new Socket(ipAddress, serverPort);

                        InputStream sin = socket.getInputStream();
                        OutputStream sout = socket.getOutputStream();
                        // Конвертируем потоки в другой тип, чтоб легче обрабатывать текстовые сообщения.
                        DataInputStream in = new DataInputStream(sin);
                        DataOutputStream out = new DataOutputStream(sout);
                        System.out.println("You are connected to " +
                                address + " and port " + serverPort);
                        connected = true;
                    } catch (Exception x) {

});

oK.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            if(groupTextField.getText().equals("")||nameTextField.getText().equals("")
                    ||surnameTextField.getText().equals("")
                    ||passwordTextField.getPassword().length == 0)
            new Error("Empty error","One or all fields is empty,please enter the information");
            else {
                if (!Arrays.equals(passwordTextField.getPassword(), passwordConTextField.getPassword()))
                    new Error("Password Error","Passwords do not match, enter the same password");
                 else {
                    String queryCheck = "select Groups,Name,Surname from clients";
                    String query = "INSERT INTO Clients.clients(Groups,Name,Surname,Password) " +
                            " VALUES ('" + groupTextField.getText() + "','" + nameTextField.getText()
                            + "','" + surnameTextField.getText() + "','" + new String(passwordTextField.getPassword()) + "');";
                    try {
                        // opening database connection to MySQL server
                        con = DriverManager.getConnection(url, user, passwordForRoot);
                        // getting Statement object to execute query
                        stmt = con.createStatement();
                        // executing SELECT query
                         rs = stmt.executeQuery(queryCheck);
                        while(rs.next())
                        {
                            if(rs.getString(1).equals(groupTextField.getText()) && rs.getString(2).equals(nameTextField.getText())
                                    && rs.getString(3).equals(surnameTextField.getText()))
                            {
                                new Error("Row error","The same account is already exist");
                                break;
                            }
                        }

                        stmt.executeUpdate(query);
                    } catch (SQLException sqlEx) {
                        sqlEx.printStackTrace();
                    } finally {
                        //close connection ,stmt and resultset here
                        try {
                            con.close();
                        } catch (SQLException se) { /*can't do anything */ }
                        try {
                            stmt.close();
                        } catch (SQLException se) { /*can't do anything */ }
                        try {
                            rs.close();
                        } catch (SQLException se) { /*can't do anything */ }
                    }
                }
            }

        }
    });