A communication system including an image processing apparatus configured to receive N-th operation definition information from a server, when the N-th operation definition information includes an option selecting instruction, set a user interface to be allowed to accept an option selecting operation, and transmit to the server, next-operation request information being for requesting the server to transmit (N+1)th operation definition information, when the N-th operation definition information includes an operation instruction, control an image processor to perform an operation as instructed by the operation instruction, set an apparatus-side network interface to be allowed to receive from a mobile terminal device, shortcut information indicating that a coordinated operation is started from an M-th unit operation of the plurality of unit operations, and when receiving the shortcut information from the mobile terminal device via the apparatus-side network interface, transmit the shortcut information to the server via the apparatus-side network interface.