SocketUtils.java

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;

public class SocketUtils {

    public static int findFreePort(int minPort, int maxPort) {
        for (int i = minPort; i < maxPort; i++) {
            if (isPortAvailable(i)) {
                return i;
            }
        }
        throw new IllegalStateException("Could not find a free TCP/IP port in range between " + minPort + " and " + maxPort);
    }

    public static boolean isPortAvailable(int port) {
        try(ServerSocket serverSocket = new ServerSocket()) {
            serverSocket.setReuseAddress(false);
            serverSocket.bind(new InetSocketAddress(InetAddress.getByName("localhost"), port), 1);
            return true;
        } catch (Exception ex) {
            return false;
        }
    }
}