California Code, Family Code - FAM § 2331

(a) A copy of the petition, together with a copy of a summons, in a form and content approved by the Judicial Council, shall be served upon the other party to the marriage in the same manner as service of papers in civil actions generally.

(b) If the parties file a joint petition and joint summons, in a form and content approved by the Judicial Council, the joint petition shall be deemed to be served on both parties upon the filing of the joint petition with the court and both parties shall be determined to have appeared in the matter.