DOTS MULTIPLAYER

This is an attempt to create a dots based multiplayer game using Unity and to learn how to make things to scale. The eventual goal is to re-create Realm of the Mad God, but i am sure you can use this repo to figure out how to do a few of the multiplayer systems.

How it works

This top level architecture is inspired from the multiplayer sample project inside the not-yet released unity.transport package. But unlike the ICustomBootstrap method to initialize the different worlds, we use Zenject based Initialize function to create the server and client worlds. The settings are stored in a scriptable object which is injected into the WorldManager. The ClientWorld makes a copy of the InitializationGroup, SimulationGroup and PresentationGroup from the DefaultWorld. The PresentationGroup is added only if you're the "user" and not a bot. You can set clientCount to spawn multiple clients. The ServerWorld makes a copy of InitializationGroup and SimulationGroup. Custom worlds cannot call update on their systems so these custom world systems are added back to the DefaultWorld systems update cycles.

Data Flow Overview

LiteNetLib is used to create the server and client network peers and are completely contained in the ClientNetworkSystem and ServerNetworkSystem. Communication with and to these systems is done through custom component data objects in their respective worlds. We use MessagePack-CSharp to serialize the data between the worlds. Right now only two objects are exchanged between the clients and server.

1. The ClientInputData which is the per frame info about the user's input + their input tick. This is sent from Client -> Server.
2. The WorldState which is the snapshot per client (relative to the player input index).

Next Steps

1. Generalize the network data from only input data and world state to general rpc objects.
2. Send deltas instead of world snapshot.
3. Physics, obstacle detection.
4. Server side NPCs.
5. Diconnect/Re-connect handling.