By the sounds of it this is not online as in online game features or even network play, so this is not for games with network or online play modes at all, but more to have a player 2 port over the internet a bit like the way most older online multiplayer support works for emulation rather than local network or online network play
MGS3 servers are long gone now anyway, though I still have the Sub version of the PS2 game anyway (that whole 3 DVD set) I'm am sure that never had a local network mode, but can check if I felt the need
even later releases of MGS3 on PSVita and PS3 [Part of a collection of MGS games] (happen to have those also) does not include MGS3 online mode or the other mini game I loved, something to do with Monkey Hunting that I felt they could of included, though yes a little gimmicky, it was still fun.