A communication system capable of carrying out communication between terminals within different local systems via a plurality of relay servers. The first terminal is connected to the relay server, and the communication with the first relay server is made practicable. In the same manner, the second terminal is connected to the second relay server, and the communication with the second relay server is made practicable. When a connection demand with the second terminal is transmitted to the first relay server from the first terminal, the first relay server forwards the connection demand to the second relay server, and the second relay server notifies the connection demand to the second terminal, and the communication between the terminals is made practicable. Then, when the data is transmitted from the first terminal to the second terminal, the data is forwarded to the second terminal through the first and second relay servers. Accordingly, the communication can be carried out between the terminals within the local systems connected to different relay servers.