code: private ServerAddress createServerAddress(String group) {
  		final Setting setting = checkSetting();
  
  		if (group == null) {
  			group = StrUtil.EMPTY;
  		}
  
  		final String tmpHost = setting.getByGroup("host", group);
  		if (StrUtil.isBlank(tmpHost)) {
  			throw new NotInitedException("Host name is empy of group: {}", group);
  		}
  
  		final int defaultPort = setting.getInt("port", group, 27017);
  		return new ServerAddress(NetUtil.buildInetSocketAddress(tmpHost, defaultPort));
  	}
docs: 创建ServerAddress对象，会读取配置文件中的相关信息
  
  @param group 分组，如果为null默认为无分组
  @return ServerAddress