To call and shift an application of a corresponding server as the application program of a client is shifted when dynamically replacing the application program without interrupting it.

Client process 2 is equipped with an AP management table initialization means 22 for generating and initializing a AP management table 21, an AP generation registration means 23 which refers to a generation information table 11, acquires generation information for a corresponding logical application program and writing it on the AP management table, an AP calling means 25 which refers to the AP management table, loads the logical application program from an AP storage file 20, and selects a generation of the corresponding application program, and a demand transmission means 27 for generating a transmission telegram 30 including a generation selected by the application program and transmitting the telegram to the server.