(a) Whenever under this article service or the giving of any notice is required or permitted to be made upon a party and the party is represented by an attorney, the service shall be made upon the attorney unless service upon the party himself is ordered by the court. Service of all notices and other papers hereunder and service of motions for new trial, motions in arrest, motions for judgment notwithstanding the verdict, and all other similar motions, orders, and proceedings may be made by the attorney or party filing the notice or paper, in person or by mail, and proof thereof shown by acknowledgment of the attorney or party served, or by certificate of the attorney, party, or other person perfecting service. Service of any paper, motion, or notice may be perfected either before or after filing with the clerk thereof; and when service is made by mail it shall be deemed to be perfected as of the day deposited in the mail. Where the address of any party is unknown and the party is not represented by an attorney of record, service of all notices and other papers referred to above may be perfected on the party by mail directed to the last known address of the party.

(b) Service of any notice, motion, or other paper provided for in this article may be waived or acknowledged either before or after filing.