Abstract: A streaming data relay apparatus is disclosed including: an RF module for receiving streaming data transmitted in unicast format from a wireless gateway apparatus; an Ethernet connection module; and a control unit for transmitting the streaming data in unicast format to multiple client devices corresponding to a same multicast group via the Ethernet connection module; wherein when a first client device out of the multiple client devices requests to leave the multicast group, the control unit transmits the physical address of the first client device to the wireless gateway apparatus through wireless transmission via the RF module.