In a relay communication system in which remote LANs communicate with one another beyond a WAN, respective apparatuses confirm a virtual network environment of the relay communication system in real time. Relay servers relay mutual communication between client terminals. The relay server creates information shown below, and allows the whole of the relay communication system to share the information: a relay group information indicating virtual private IP addresses of the relay servers and a connection establishment state therebetween; and a relay server information indicating a virtual private IP address and connection establishment state of a client terminal capable of communicating with the relay server. The respective apparatuses in the relay communication system can share the information regarding the virtual private IP addresses and connection establishment states of all the apparatuses, and can flexibly execute communication in which the virtual private IP addresses are designated as destinations for communication.