PURPOSE: To easily uniformize an unbalanced communication load even when the communication load at each port of a server is unbalanced.

CONSTITUTION: At least one port of a server S and stations T1-Tm being clients of the server S are interconnected by an indefinite communication network 1. other optional communication path than a communication path used at present is used freely for communication between each of ports P1-Pn of the server S and the stations T1-Tm in this indefinite communication network 1. Moreover, when all the stations are included in this indefinite communication network 1 and the stations desire mutual communication, the communication is directly executed not through the server S and efficient communication is attained without imposing useless load onto the server.