Port scan

PortScan.java

import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;


public class PortScan {

    public static void main(String... args) {
        String host = args[0].equals("-") ? "localhost" : args[0];
        int portStarting = Integer.parseInt(args[1]);
        int portEnding = args.length >= 3 ? Integer.parseInt(args[2]) : portStarting;

        for (int currentPort = portStarting; currentPort <= portEnding; currentPort++) {
            Registry registry = null;
            String[] list = null;
            try {
                registry = LocateRegistry.getRegistry(host, currentPort);
                list = registry.list();
            } catch (RemoteException e) {
                // Si hay bronca es porque no se pudo conectar, no me interesa hacer nada
            }
            if (list != null && list.length != 0) {
                System.out.println("\n" + host + ":" + currentPort);
                for (String name : list) {
                    System.out.println("  - " + name);
                }
            }
        }
    }
}

Obtener nombre de los puertos del 5 al 10 en localhost
java PortScan - 5 10

Obtener nombre de los puertos del 5 al 10 en el servidor 123.123.123.123
java PortScan 123.123.123.123 5 10

Obtener nombre del puerto 5 en el servidor 123.123.123.123
java PortScan 123.123.123.123 5