PURPOSE: To reduce the burden at sites by generating a transportation table at the time or transporting a port to perform communication without complicated processing then.

CONSTITUTION: The transportation table including a site number S1 and a local number L11 is generated in a site S1 of the transportation source. A port L21 is generated in a site S2 of the transportation destination. The transportation table including the site number S1 and the local number L11 is generated in the site S2 also, and information of a transportation local number L21 and a transportation site number NULL(0) is added. Next, the transportation site number of the transportation table is set to S2. Messages queued in the port L11 of the site $1 are transferred to the port L21 of the site S2. The port L11 of the site S1 is deleted. Thus, the position of the site is easily detected.