udemy-mirror-course

https://www.udemy.com/course/unity-multiplayer

Learning how to make multiplayer RTS

Instructor Youtube Channel: https://www.youtube.com/c/DapperDinoCodingTutorials

Takeaways

Section 1 - Introduction

• How network manager works
• What are network identities
• Authority
  • By default, server has authority. A client can obtain authority over an object. Then that client is able to request changes to that object state.
  • Assigned during spawn or with AssignClientAuthority method
• SyncVars
  • When written in the server, broadcast changes to all clients
  • Callback - Can hook to a method (using nameof(Method) as the hook parameter). Used to run a method in the client when the SyncVar is updated.
• Command
  • Called by a client, executed in the server
  • Can bypass server authority with parameter
• ClientRcp
  • Method is ran on all clients when called by the server.
• TargetRcp
  • Similar to ClientRcp, but can restrict who receives the calls.
  • Only targeted clients receives the call. By default, it's the object owner.
• Unity Callback with Authority
  • Callbacks OnStartAuthority and OnStopAuthority, only execute if the client has authority over the object
• ClientCallback attribute limits Unity default callbacks to be run on client only. ServerCallback for server.
• Can create spawn points using NetworkStartPosition - And assign algorithm (Random or Round Robin) in the network manager.

Section 2 - RTS Game

Project Setup and Unit Spawning

Mirror

• Player network, with just network identity
• Spawner network object also belongs to a player
• Spawned object uses Spawner connection to give authority to the right client.
• Add spawner object as a new player gets added. conn.identity maps to the player object.

Input System

• Add EventSystem to scene for detecting IPointerClickHandler event.
• Update EventSystem script (New Input System)
• Add Physics Raycaster to camera

Networking

• Code running on the server in a component that also exist in client -> NetworkBehaviour
• Adding prefix Cmd and Rpc to remote methods help a lot on code readability.
• connectionToClient in NetworkBehaviour is a good way to figure out if objects belong to the same user
• Network manager has a singleton access.
• When implementing a lobby, we need to remove the Offline Scene and Online Scene references from network manager.
  • This breaks everything. You need to spawn things (except the player) manually after changing to the proper scene.
• When overriding some NetworkManager methods, we MUST call the base method. I did for only some, and forgot for OnServerConnect. This made the server stop spawning player game objects.
• The instructor made the camera a NetworkBehaviour. For the game we do in the course, it could totally be a local cotntrolled object, but it might be useful for an actual RTS if we want to be able to control the client camera from the server side.

Authority

• Also has OnStartAuthority and OnStopAuthority callbacks
  • Called on clients that have authority over that object when you get authority or lose authority over it

Steam Transport

• https://mirror-networking.gitbook.io/docs/transports/
  • https://mirror-networking.gitbook.io/docs/transports/fizzysteamworks-transport

Major Issues

• I had this misconception of trying to get the player that owned certain object on client. However this is more like a server-side logic. So instead I had to make a network behaviour get the value server side and then only set the value to a syncvar to the clients. E.g. team color.
  • Idea for this: Teams should have material for their colors. Then each unit only gets the team id from the server side, and fetches the material locally.

Extra

• TIL RectTransformUtility is nice
• Looks very similar with https://docs-multiplayer.unity3d.com/, need to experiment with it sometime.

Out of course scope notes:

• NavMesh generation at runtime: https://learn.unity.com/tutorial/runtime-navmesh-generation