Some big MMORPG games like World of Warcraft has a lot of, i suppose illegal, Private Servers that people play on for various reasons, for example to play for free. But Im wondering how does that really works? How are they able to host and modify games they shoudn't be able to access? Do they somehow hack to access the source code of the game? Because I suppose building the game from scratch themselves is a bit too ambitious...
Hope this thread doesn't violate any rules as Im just curious on how this can be possible
Neither. They rebuild the server side from information they can get while playing. In mmos most of the "content" is on the client side (all the models / world , in current mmo even items). So you use your normal client and connect to their servers, so server part is what they have to emulate, this is done in multiple steps, let's see what you need to rebuild a server without access to source code. 1) Packet sniffing and reverse engineer how the game client and server communicates, to see what your "server" will need to answer when asked by a client. This is a technical step, simply figuring out packet formats & such 2) Forumlas, lots of them, often guessed, to be able to reproduce the part of the gameplay that is done on the server (for exemple, damage calculation) 3) Missing data, some emulators get it from players running programs logging what the users receive from the server, this is serverside only data that is never on the client except when sent by the server (or deduced from other data sent by the server), for example spawn point and spawn time, monster drops and droprate etc, if you make an emulator and people kill monster X, you need to know how long untill it repops, what it drops and what it's droprate is like to emulate the server 4) Maintaining and saving state, this is the server part in itself that you need to re code from scratch, from the info you grabed in the first 3 parts.
That's pretty much it, so yes basically they recode everything that happens on the real MMO servers, sometime to act exactly the same, sometime throught guesswork, to end up with something that feels "kind of" the same when played from the real game client.
