Service of process upon a partnership or limited partnership may be made by

    (1) leaving a summons and a copy of the complaint with any general partner personally, or

    (2) leaving a summons and a copy of the complaint with a person in charge of a partnership office or business establishment at such office or place of business and sending a summons and a copy of the complaint by registered mail, addressed to any general partner at his usual place of abode or last known address.