private ArrayList<String> findUsersForGame(String selfId) {
        utils.resources.Game gameResource = (utils.resources.Game)Resources.getInstance().getResource("data/game.xml");
        ArrayList<String> playersId = new ArrayList<>();
        playersId.add(selfId);

        for (String userId: sessionIdToUserSession.keySet()) {
            if (!userId.equals(selfId)) {
                UserSession userSession = sessionIdToUserSession.get(userId);
                if (userSession.isUserOnline() && userSession.getStatus() == UserSession.Status.waitingPlayer) {
                    playersId.add(userId);
                    if (playersId.size() >= gameResource.getNeedPlayers())
                        break;
                }
            }
        }

        if (playersId.size() < gameResource.getNeedPlayers())
            return null;
        return playersId;
    }