I wrote a code for reading a local JSON-File and putting it on port 9000. After a set time limit the class PutJsonOnline should be terminated. The terminate method will be called and the access to port 9000 should be cut. However, after calling the terminate method, I still can access port 9000. Can anybody help me terminating the connection to port 9000 properly?

import static spark.Spark.*;

import java.io.InputStream;
import java.util.Scanner;
import java.util.concurrent.CountDownLatch;

public class PutJsonOnline {

    private static volatile boolean isRunning = false;
    private static final CountDownLatch latch = new CountDownLatch(1);
    private static Thread serverThread;

    public static void main(String[] args) {
        startServer();
    }

    public static void startServer() {
        serverThread = new Thread(() -> {
            port(9000);

            // Define endpoint to serve JSON data
            get("/data", (req, res) -> {
                if (!isRunning) {
                    halt(403, "Server is not running");
                }
                res.type("application/json");

                // Read JSON data from file in resources directory
                InputStream inputStream = SendJsonToServer.class.getResourceAsStream("/data.json");
                String json = readFromInputStream(inputStream);

                return json;
            });

            // Log server start
            System.out.println("Server started on port 9000");
            isRunning = true;
            latch.countDown(); // Signal that the server has started
        });

        System.out.println("Starting server thread...");
        serverThread.start();
        try {
            latch.await(); // Wait for the server to start
            System.out.println("Server thread started and latch released.");
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }

    private static String readFromInputStream(InputStream inputStream) {
        if (inputStream != null) {
            try (Scanner scanner = new Scanner(inputStream).useDelimiter("\A")) {
                return scanner.hasNext() ? scanner.next() : "{}"; // Return empty JSON object if file is empty
            }
        }
        return "{}"; // Return empty JSON object if file is not found
    }

    public static void terminate() {
        System.out.println("Terminating server...");
        isRunning = false;

        // Stop the Spark server
        stop();

        // Wait for Spark to stop
        awaitStop();

        // Ensure the server thread is stopped
        if (serverThread != null && serverThread.isAlive()) {
            serverThread.interrupt();
            try {
                serverThread.join();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }

        System.out.println("Server stopped.");
    }
}