A system capable of switching terminals while continuously receiving data on terminals monitored by a relay device such as a gateway. In devices such as a gateway for relaying data, the session status of the terminal under control is monitored and the relay processing status of data received externally over a network is changed according to requests such as pause, list, resume and call from a terminal, and the dynamic data address is changed or the relay of data is temporarily halted (pause). The present structure allows the user (client) to change the terminal receiving the data and change the receive processing status so that data can be continuously received on the terminal used after switching terminals.