Interesting idea, but consider this: In massively multiplayer games, you''ve usually got a persistent world. With persistent worlds, cheating is a much more significant problem than it is with discrete game sessions.

Basically, you''d open the door for a great number of cheats. Plus, you''d surrender control of the online world, so you couldn''t really influence it once the game has begun.

Maybe there are solutions to these problems, but running a server farm is probably cheaper than fighting an uphill battle against exploits and other problems in the long run. Who knows...

cu,
Prefect

I did alot of research studying just such an implementation for MMORPGs. I envisioned a central State server where state was persisted but the actual gamestate would be running in various peer-to-peer sessions that would update the main server''s persisted state every so often. As people moved around the game world they would move between different peer to peer sessions. The holy grail of MMORPG''s I suppose. A virtually Unlimited Scalability model.


There was one problem, however, no way to guarantee security. I explored various solutions. Having each session be a simultaneous simulation (like AOE) where clients were validated against each other. The only problem with that is someone is bound to find out the validation mechanism and then they and a group of their friends could hijack a section of the game state and make all the changes they wanted, which would then be persisted to the main server.

I though of ways to make this more difficult, like randomly hosting small portions of a games state on the state server to make sure that none of the clients in a peer to peer session were cheating, but even then they could detect when the server made a connection and give it the responses it was expecting, while having their way with the game state.

What I came to realize is that a MMORPG system must be two things, it must be Secure, and it must be scaleable in that order. Any time you trust clients with a portion of the gamestate, like in a peer to peer environment you are no longer secure. The more popular your game becomes the more motivation people will have to hack it, it''s only a matter of time. Once people have hacked your game and you have uber characters walking around who cheated to get there, no one will want to play your game. All your scalability is for nothing if no one will play your game. Thus scalability is second only to security.

If you’re going to build a persistent world, start with a secure model e.g. Client Server. Obey all the rules. Never trust the Client with anything. Assume that hackers have the source code for your client and that they can see everything it can. After you''ve dealt with security, you can start with scalability. A O(n) scalability factor is pretty good under these circumstances.

When you’re talking about persistent state worlds Security is an absolute must! You’re expecting your players to invest time and energy to build up their characters and possessions in this world. If some hacker starts on Monday and is level 200,000 on Wednesday and killing all the people who have invested weeks/months/years acquiring their skills and items in the traditional manner, all your traditional players are going to quit in disgust.

The motivation for hackers to hack persistent state games is much greater then in games where the gamstate is session based, like a starcraft or AoE. If someone hacks the gamestate in an RTS match, the other players can just quit and go join some other game. The hack does not result in any lasting benefit to the hacker. Not so with persistent state games like today’s MMORPGS. Once a hacker has hacked the system his changes to the gamestate are permanent. He will have a continuing advantage over all the other players he is competing against. Thus his motivation to hack is much higher.

People quit playing Asherons Call in droves after the “GEAR” hacks game some player’s ridiculous competitive advantages on the PvP servers. If you think that no one will hack your persistent MMORPG world because you make it really easy to do so. You’re sadly mistaken. What will happen is that people will all max out their levels and experience, play for a few days and get bored because there is no inherent value in fighting monsters or leveling up. Why work up the hard way when everyone else is just modifying their characters in the editor you shipped with the game. It is this whole concept of building your characters faster then everyone else that drives people to play these MMORPGS for countless hours. It’s because of their belief that everyone must follow the same rules of progression that their advancement even has value. If some newbie can just get to the same level by editing his character then advancement will be meaningless and no one will play for longer then a week.

If I haven’t convinced you go ahead and try to implement a persistent state massively multiplayer game with absolutely no regard for security. I think you’ll soon understand what I’m talking about

That’s fine for if a client changes his information while offline. (although this situation would likely never occur because the Client''s stats and inventory are populated from the server when they connect) But consider this, and this is what I was referring to above. What if the client changed his stats while playing the game, or perhaps gave himself some uber items. When the user logged out of the game, his new stats and items would be saved to the server. The server would have no way of knowing if the client achieved those stats and items legitimately or by hacking. Sure you could set limits on how many levels you could gain in one session, but hackers would rapidly figure out the levels, and how to max them out every time they played. Once you trust the gamestate to live on the client, you are no longer in control, the server is at the mercy of the clients.