A server/client system provides packet communications between a server and a client by way of a network such as the Internet. The server inputs data such as MIDI data in a sporadic manner while storing timing data representing their input timings. Then, the server performs packetizing of the sporadically input data, which accompany the timing data and are subjected to transmission to the client. The client receives the packetized input data and then outputs them at timings based on the timing data. Thus, it is possible to completely secure the same time relationship of data during transmission and reception of the sporadically input data even though the client differs from the server on a time-axis basis.