I constantly (every time i look) have some strange unknown IP in the list of active connections, see picture

.
I have never seen any activity from/to this IP. I have relativelly secure wifi

, and this IP never appear as wireless client, so i do not think this is wifi intruder. And this IP does not belongs to my network IP range, which makes me confusing even more

. Can somebody explain me what the hell is this?
Gargoyle 1.5.4, router netgear WNDR3700v2
update: last column, "UDP Cxnx", is not visible clearly, there is "1". And number of connections never change, at least i have never seen.