A communication system including an image processing apparatus configured to, in response to receiving acquisition instruction information from a server via indirect communication, receive authentication information from an information processing terminal device via near-field wireless communication, transmit the received authentication information to the server via the indirect communication, and in response to receiving communication instruction information, which indicates a method for data communication with a service providing apparatus, from the server via the indirect communication, perform data communication with the service providing apparatus in accordance with the received communication instruction information.