On early-days facebook you could "poke" someone. Like a virtual empty message, it had no meaning or "baggage" linked to it, other than that the poke-er was thinking of the poke-ee at that moment.
About a decade before that, we kids basically only had SMS text messaging, and it was very expensive in my country, mobile data doubly so. There was however a "please call me" feature, where you could send a "please call me" text to a friend free of charge. We used to send please call me's to one another all the time, not because we wanted to be called, it was just the cheapest form of digital communication.