A non-transitory computer-readable medium storing program instructions that, when executed by processing circuitry, cause the processing circuitry to perform a method of monitoring usage of an image output device, the method comprising:
- receiving, from the image output device, a real-time status message transmitted using an Internet application-layer protocol over a network, the received message including a job identifier identifying a print job and resource usage information for the print job, wherein the print job was processed by the image output device for a registered user of the image output device;
- extracting, from the received message, the job identifier and the resource usage information;
- calculating, based on the extracted resource usage information and usage information of the registered user stored in a memory, a total resource usage of the registered user;
- determining whether the calculated total resource usage of the registered user reaches a predetermined threshold;
- and
- transmitting a message over the network to a predetermined destination, when it is determined in the determining step that the calculated total resource usage of the registered user reaches the predetermined threshold.