Patent ID: 8521847

Claim:
A network system comprising: a controller including a processor and memory; and a plurality of terminals connected to said controller via a network, each terminal including a processor and memory, wherein said controller comprises a first communication unit configured to communicate with said terminal via the network, a first request unit, a counting unit, a terminal number determination unit, a limited time determination unit, and a second request unit, each of said terminals comprising a second communication unit configured to communicate with said controller via the network, a first response unit, a waiting time determination unit, and a second response unit, said first request unit of the controller configured to send a first request signal to the plurality of said terminals via said first communication unit, the first request signal including probability information indicative of a predetermined probability, said first response unit of each terminal configured to, upon receiving the first request signal via said second communication unit, send a first response signal to said controller via said second communication unit at the probability indicated by the probability information included in the first request signal, said counting unit of the controller configured to count the first response signals received via said first communication unit, and output the obtained number of the first response signals, said terminal number determination unit of the controller configured to determine a total number of said terminals responding to said controller on the basis of the probability and the number of the first response signals obtained from said counting unit, said limited time determination unit of the controller configured to determine a limited time period on the basis of the total number of said terminals determined by said terminal number determination unit of the controller, said second request unit of the controller configured to send a second request signal to the plurality of said terminals via said first communication unit, the second request signal including limited time information indicative of the limited time period determined by said limited time determination unit, said waiting time determination unit of each terminal configured to, upon receiving the second request signal via said second communication unit, select a waiting time period in a random manner from time periods not greater than the limited time period indicated by the limited time information included in the second request signal, and said second response unit of each terminal configured to send a second response signal to said controller via said second communication unit after a lapse of the waiting time period.