ObjectStream:

public class ObjectStreamServer {
    public static void main(String[] args) throws IOException {

        if (args.length != 1) {
            System.err.println("Usage: java KnockKnockServer <port number>");
            System.exit(1);
        }

        //zbiera numer portu po którym ma się łączyć
        int portNumber = Integer.parseInt(args[0]);

        try (
            //tworzy socket dla danego portu
            ServerSocket serverSocket = new ServerSocket(portNumber);
            //czeka na połączenie
            Socket clientSocket = serverSocket.accept();
        ) {
            Generator generator = new Generator();
            List<Krawedz> graf = new ArrayList<Krawedz>();
            graf = generator.generuj();
            int[][] tab = generator.doTablicy(graf);

            ObjectOutputStream ol = new ObjectOutputStream(clientSocket.getOutputStream());
            ol.writeObject(tab);
            clientSocket.close();

        } catch (IOException e) {
            System.out.println("Exception caught when trying to listen on port "
                + portNumber + " or listening for a connection");
            System.out.println(e.getMessage());
        }
    }
}

XStream:

public class XMLServer {
    public static void main(String[] args) throws IOException {

        if (args.length != 1) {
            System.err.println("Usage: java KnockKnockServer <port number>");
            System.exit(1);
        }

        //zbiera numer portu po którym ma się łączyć
        int portNumber = Integer.parseInt(args[0]);


            //tworzy socket dla danego portu
            ServerSocket serverSocket = new ServerSocket(portNumber);
            System.out.println("Server up & ready for connection...");
            //czeka na połączenie
            Socket clientSocket = serverSocket.accept();
            ObjectOutputStream ol = new ObjectOutputStream(clientSocket.getOutputStream());
            System.out.println("Sending information...");

            Generator generator = new Generator();
            List<Krawedz> graf = new ArrayList<Krawedz>();
            graf = generator.generuj();
            int[][] tab = generator.doTablicy(graf);

            XStream xstream = new XStream();
            //String abc = "Cześć to ja";
            //System.out.println(abc);
            String xml = xstream.toXML(tab);
            //System.out.println(xml);
            ol.writeObject(xml);
            System.out.println("Closing the connection...");
            clientSocket.close();
        /*
        } catch (IOException e) {
            System.out.println("Exception caught when trying to listen on port "
                + portNumber + " or listening for a connection");
            System.out.println(e.getMessage());
        }*/
    }
}