public class GameServer extends Thread {

    private ServerSocket server;

    public GameServer() throws IOException {
        try {
            doPortForwarding();
            server = new ServerSocket(10000);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    public void run() {
        while (true) {
            try {
                Socket s = server.accept();
                System.out.println("Accepted");
                //Do things...
            } catch (IOException ex) {
                Logger.getLogger(GameServer.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

    private void doPortForwarding() throws UnknownHostException {

        PortMapping[] desiredMapping = new PortMapping[1];
        desiredMapping[0] = new PortMapping(10000, InetAddress.getLocalHost().getHostAddress(),
                PortMapping.Protocol.TCP, " TCP POT Forwarding");

        UpnpService upnpService = new UpnpServiceImpl();

        RegistryListener registryListener = new PortMappingListener(desiredMapping);
        upnpService.getRegistry().addListener(registryListener);

        upnpService.getControlPoint().search();
        
    }

}