/**
  * Deregistra un player dal server, rendendo nuovamente disponibile il nickname ad altri player.
  *
  * @param nickname nome del player da deregistrare
  */
 public void deregisterPlayer(String nickname) {
   try {
     server.deregister(nickname);
   } catch (RemoteException e) {
     System.out.println("Impossible to logout." + e.getMessage());
   }
 }
  /**
   * Create a MonitoredHostProvider instance using the given HostIdentifier.
   *
   * @param hostId the host identifier for this MonitoredHost
   * @throws MonitorException Thrown on any error encountered while communicating with the remote
   *     host.
   */
  public MonitoredHostProvider(HostIdentifier hostId) throws MonitorException {
    this.hostId = hostId;
    this.listeners = new ArrayList();
    this.interval = DEFAULT_POLLING_INTERVAL;
    this.activeVms = new HashSet();

    String rmiName;
    String sn = serverName;
    String path = hostId.getPath();

    if ((path != null) && (path.length() > 0)) {
      sn = path;
    }

    if (hostId.getPort() != -1) {
      rmiName = "rmi://" + hostId.getHost() + ":" + hostId.getPort() + sn;
    } else {
      rmiName = "rmi://" + hostId.getHost() + sn;
    }

    try {
      remoteHost = (RemoteHost) Naming.lookup(rmiName);

    } catch (RemoteException e) {
      /*
       * rmi registry not available
       *
       * Access control exceptions, where the rmi server refuses a
       * connection based on policy file configuration, come through
       * here on the client side. Unfortunately, the RemoteException
       * doesn't contain enough information to determine the true cause
       * of the exception. So, we have to output a rather generic message.
       */
      String message = "RMI Registry not available at " + hostId.getHost();

      if (hostId.getPort() == -1) {
        message = message + ":" + java.rmi.registry.Registry.REGISTRY_PORT;
      } else {
        message = message + ":" + hostId.getPort();
      }

      if (e.getMessage() != null) {
        throw new MonitorException(message + "\n" + e.getMessage(), e);
      } else {
        throw new MonitorException(message, e);
      }

    } catch (NotBoundException e) {
      // no server with given name
      String message = e.getMessage();
      if (message == null) message = rmiName;
      throw new MonitorException("RMI Server " + message + " not available", e);
    } catch (MalformedURLException e) {
      // this is a programming problem
      e.printStackTrace();
      throw new IllegalArgumentException("Malformed URL: " + rmiName);
    }
    this.vmManager = new RemoteVmManager(remoteHost);
    this.timer = new Timer(true);
  }