Whenever two or more persons, associated in any business, transact such business under a firm name, whether it comprises the names of such persons or not, the associates may be sued by such firm name, the summons in such case being served on one or more of the associates or as otherwise provided by rule of court; and any judgment recovered against the firm, as such, may be enforced against the firm property, and against the individual property of any of the associates who have been served with process or who have appeared in the action.