I don’t know what other games you play, but they all seem to have similar principles underlying their netcode. Think of a game like rocket league (casual mode), or fromsoftware game like elden ring, or a counterstrike game, or an MMO. You’re running it locally, on your computer, but in order for people to seamlessly drop in to an ongoing match in rocket league, or to invade/help in elden ring means there is a server side. You can join the exile’s group and jump to the area they’re in for path of exile, no extra work required on the client side. I don’t think you can even play ‘offline’ like you can in rocket league or elden ring. The counterstrike and MMO is probably the closest example, because when you login to path of exile, you are definitely logging into a server. It’s why you can see all the people in town.
I don’t know what other games you play, but they all seem to have similar principles underlying their netcode. Think of a game like rocket league (casual mode), or fromsoftware game like elden ring, or a counterstrike game, or an MMO. You’re running it locally, on your computer, but in order for people to seamlessly drop in to an ongoing match in rocket league, or to invade/help in elden ring means there is a server side. You can join the exile’s group and jump to the area they’re in for path of exile, no extra work required on the client side. I don’t think you can even play ‘offline’ like you can in rocket league or elden ring. The counterstrike and MMO is probably the closest example, because when you login to path of exile, you are definitely logging into a server. It’s why you can see all the people in town.