PPSSPP MP without Hamachi or any stuff like that?

[Threule]

Is it possible to do a MP game without setting a LAN or a Fake LAN? (AKA opening ports)

[AdamN]

It's possible using the same PC

[Adhenovan]

without LAN or VLAN then what you want to use to transport the game data?

this question not clear enough , its like questioning how to cross a sea without ship and did not tell what your preferred vehicle to cross the sea.

as long as game data can be transported from one PPSSPP instance into another PPSSPP instance its possible, no matter what the route is , Internet , LAN , Loopback address (Same PC connection) , VPN. you must ensure nothing block the data PPSSPP want to transfer / establish which is the primary issues on adhoc over internet.