A network system according to an implementation of the present invention involves: determining whether or not a matching address is found by comparing (i) an apparatus address, of an apparatus connected to an HDMI network, which is obtained via the HDMI network with (ii) an apparatus address, of an apparatus connected to another network, which is obtained via the other network (S44). Here, the matching address represents a match between the apparatuses addresses. When determining that the matching address is found, the implementation of the present invention involves determining that the terminal apparatus having the matching address is connected to a control apparatus via both of the HDMI network and the other network (S46).