A programmable logic controller system comprising: a storage unit storing a user program; a web based service control unit; a main control unit performing a scan operation based on the user program, measuring a scan time taken to perform the scan operation, and transmitting the measured scan time, service data and service request details along with a service processing signal to the web based service control unit; the web based service control unit receiving the measured scan time, the service data and the service request details along with a service processing signal and, the system being characterized in that the web based service control unit is configured to determine an amount of service data to be processed according to the scan time and process the service data based on the scan time and the determined amount of service data to be processed, or determine a priority based on the service request details with reference to a priority according to a pre-stored service, and process the service data based on the determined amount of service data to be processed and the priority based on the service request details with reference to the priority according to a pre-stored service; wherein the scan operation includes an operation of reading data from an external device and storing a result of the execution of the scan program in an output image region. a storage unit storing a user program; a web based service control unit; a main control unit performing a scan operation based on the user program, measuring a scan time taken to perform the scan operation, and transmitting the measured scan time, service data and service request details along with a service processing signal to the web based service control unit; a web based service control unit; a main control unit performing a scan operation based on the user program, measuring a scan time taken to perform the scan operation, and transmitting the measured scan time, service data and service request details along with a service processing signal to the web based service control unit; the web based service control unit receiving the measured scan time, the service data and the service request details along with a service processing signal and, the system being characterized in that the web based service control unit is configured to determine an amount of service data to be processed according to the scan time and process the service data based on the scan time and the determined amount of service data to be processed, or determine a priority based on the service request details with reference to a priority according to a pre-stored service, and process the service data based on the determined amount of service data to be processed and the priority based on the service request details with reference to the priority according to a pre-stored service; receiving the measured scan time, the service data and the service request details along with a service processing signal and, the system being characterized in that the web based service control unit is configured to determine an amount of service data to be processed according to the scan time and process the service data based on the scan time and the determined amount of service data to be processed, or determine a priority based on the service request details with reference to a priority according to a pre-stored service, and process the service data based on the determined amount of service data to be processed and the priority based on the service request details with reference to the priority according to a pre-stored service;