In order to enable downloading to a mobile printer data items from a server, a method is disclosed comprising the steps of establishing communication connection end points ("sockets"), communicating with the server, where the communication includes sending a request for authentication to the server, receiving an authentication response, requesting print data portions from the server, receiving the requested print data portions, and notifying the server after each print data portion has been printed. The method also includes the step of terminating their communication connection when a printing session ends or if an error occurs. The method constitutes a printer-server protocol.