In synchronous communication in a client-server-distributed data system, the turnaround time from when a client calls a server function until the client receives a notification of completion of the server function is reduced. A server includes a pre-processing registration section for registering pre-processing; a post-processing registration section for registering post-processing; a server command section for requesting to register the pre-processing and the post-processing; and a server function correspondence section for establishing correspondence between the pre-processing and the post-processing with a server function identifier. When the server receives a request message from a client to call a server function, the server execute pre-processing and sends a completion message including the execution result of the pre-processing to the client. After sending the completion message, the server executes post-processing.