Backend for data-driven multiplayer game

Question

I am working on a match-based (5v5) multiplayer steam game that is similar to TF2, LoL, Dota 2, etc.

I am planning a data-driven approach where character/abilities/items/etc are defined in data (JSON). This will allow for easy patching to constantly balance the game.

So I have something like the following. (obviously simplified)

{
    "Troll": {
        "name" : "Troll",
        "health" : "100",
        "abilities" : [
            {
                "name" : "ClubSwing",
                "damage" : "50"
            },
            {
                "name" : "FootSmash"
                "damage" : "100"
            }
        ]
    },
    "Orc": {
        "name" : "Orc",
        "health" : "50",
        "abilities" : [
            {
                "name" : "SwordSwing",
                "damage" : "10"
            },
            {
                "name" : "ArrowShoot",
                "damage" : "25"
            }
        ]
    }
}

I am wondering what the best practice way is for storing this data. I obviously can't store it client-side or the player will be able to cheat. Is it normally stored in the database? I haven't setup any backend for my game yet. Should I setup a nodejs server with a nosql database like mongodb to be the master of this data? And then build a REST API on top of that for reading this data?

I also need to write some things to a database. Such as the users rank, items, game stats, etc.

Would it be better to have two separate databases? One for reading gameplay data like I have above and another reading/writing user information (stats, rank, items, etc.)

Or would it be wiser to use a single database? Would you recommend nosql or sql based?

Note: The game engine I'm using is unreal engine 4. Currently I am using a listen server (peer-to-peer), but think it may be necessary to eventually use the dedicated server instead.

Answer 1

You probably do want to communicate to this information to the client so that they are able to view it. You can treat the client as a dummy terminal though with sparkly representation and have a "neutral" server as the authority.

Lets consider League of Legends in this context.

At the beginning of the game, each client connects to Riots servers. Every time a player moves or attacks, the client plays the animation and sends the action to the server. The server calculates the outcome and sends it to the relevant clients. If you broadcast all information to all clients then you are leaking in the sense that a client can know what is occurring in the fog of war and they should not be able to. The information transmitted affects the game state.

It is worth doing some calculations client-side though such as collision detection to prevent walking through walls or minions. This offloads some non-critical calculations and decreases latency. This does mean a client could allow itself to walk through walls, however because movement affects game state the server would still be aware of it so you could detect this kind of "attack".

In summary, the server is the final authority of the game state so it would be best to store data on the server. NoSQL vs a relational database is up to you, but odds are you can use a relational database will preform satisfactorily.

Tou most likely want to implement a binary network protocol as opposed to a textual one. This allows you to decrease the amount of data sent to convey the same information. Consider the following example, player A attacks player B. Please note this is contrived and does not include any method of ensuring message integrity.

Text Protocol Message [size=10B]: A attack B

Binary Protocol Message [size=3B]: 0x1 0x1 0x2 -

This link discusses the LoL protocol a bit, https://nelsonslog.wordpress.com/2014/08/07/league-of-legends-game-protocol/ .

Answer 2

I wouldn't store them on clients, or even ship that information with game. If security is your main concern, fetch all informations required at the beginning of the game (from a database), store them temporarily, and delete them after the game session ends.

You can also cross-check local data with database during gameplay if you want an extra layer of security.