MMO Client / Server Architecture (NoSQL)

Question

The main aim is to keep the games variables server-side for obvious security reasons. I believe having server-side code to check before updating the games database values will protect me from classic game hacking methods.

To avoid clients sending direct updates to the database, the server first validates the clients requested actions.

The database keeps track of every Mobile & Item

The Server has all the game-logic

The clients simply render and work as controllers that send the server actions that wont occur unless validated by the servers logic.

Clients should only send the server "Action Request"

Server then checks the "Action Request" with two possible outcomes :

1. Valid Request : Update DB and Re-send updated data to Clients for post-processing.
2. Invalid Request : Notify the client that the Request was invalid.

I need to know if im thinking in the right tracks. Thanks.

Answer 1

It isn't necessarily as clean cut as you expressed but in overly simplified terms and generalized notions, you are on track.

The thing to remember is that the client expresses it's intent to perform some operation. Some operations are entirely authoritative by the server. In these cases, the server must respond before the client can proceed. This works well for turn based or critical operations such as trading items within a game, inventory updates, etc. But this type of behavior isn't appropriate in all cases.

In the case of movement, it's often a better approach to allow the client to express intent to the server and simply allow the server to veto an operation should it deem the action invalid. In this case, the client begins to move as soon as the user presses the movement keys, the server simply can tell the client to back to position x, y, z if it determines the client is moving too fast or moved to an area they aren't suppose to be within. The server still is authoritative, but allows the client to provide a better user experience in exchange for a bit more complicated interpolation and handling of error responses.

Answer 2

You should take a look at how games like Minecraft, Halflife, and World of Warcraft handle this, most games take the simulated client input actions and send them to the server and simulate the world on both the client and server and correct when the simulations differ by correcting the client state to match the server state. Here you can see the entire current Minecraft protocol.

Also, given that you are interested in making an MMO, that usually contains a fair amount of relational data that may be useful to query through, I would use MySQL or another RDBMS and then use a Key Value store like Redis for simple things you will never have to search/query over and for a second layer of cache below your game server's memory cache (or just use Redis and save yourself the effort of building a memory cache for your game state).

Since you're developing an MMO, it would do you a great deal of good to look through the ArcEmu source code, ArcEmu is an open source World of Warcraft server and demonstrates everything you need to know to build an MMO server.