Patent ID: 7085809

Claim:
A communication system having a client terminal, a server and a communication link, the communication link passing link requests from the server to the client terminal without charging communication costs, the communication link charging communication costs for links which are established between the client terminal and the server, the communication system keeping identicalness between data in the client terminal and data in the server through the communication link, the communication system comprising: data transmission means for sending data from the server to the client terminal through the communication link, when the client terminal accepts a first link request; signal transmission means for sending a second link request from the server to the client terminal informing the client terminal of the status of the data in the server at a predetermined timing, the second link request being sent from the server to the client terminal through the communication link; receipt type determination means for determining whether a link request is transmitted from the data transmission means or the signal transmission means; and connection control means for establishing a link and accepting data sent by the data transmission means in the client terminal, but not establishing a link in response to the second link request sent by the signal transmission means, whereby a status of identicalness between the data in the client terminal and the data in the server is monitored in the client terminal without incurring communication costs.