Notes on Multiplayer

Shift F1 to toggle between multiplayer views
Game Instance :
Game instance created when game starts and lasts until that game executable closes, persisting across level changes and joining sessions etc.
Game instance is only aware of its own executable. Does not have any connection between server and clients. Lives only on the client.
Authoritative actor, live normally on the server.
Actor Role and RemoteRole ; https://docs.unrealengine.com/en-US/Gameplay/Networking/Actors/Roles/index.html
Server has the authoritative gamestate https://docs.unrealengine.com/en-US/Gameplay/Networking/Overview/index.html
Automatous Proxy : which is an actor on a network client that is controlled by a user on that client.
Simulated Proxy : see https://answers.unrealengine.com/questions/897406/autonomous-proxy-meaning.html
https://docs.unrealengine.com/en-US/Gameplay/Networking/Actors/Roles/index.html
BP Setting Replicate
BP Repnotify : When variable is changed, function is fired to tel al clients that something has changed. In the example only the server can changes the variable health at the clients
BP setting Replicate Movement.
BP setting Conditional Property Replication
With projectile, the client has authority over the projectile and sends a message to the server. So the other clients now a projectile is coming.
Healthbar is set at Character!
Hud, animation, particle systems, physics, sound effects does not replicate
Replicating Functions in Blueprints There are 3 primary types of replicated functions: Multicast, Run on Server, and Run on owning Client. Multicast functions should be called on the server, where they are executed, and then forwarded automatically to clients. Server functions are called by a client and then only executed on the server. Client functions are called by the server and then only execute on the owning client.
Is for example used with weapons.
Weapon is set at character
Spawn and Destroy an Actor with Blueprint Set owner and instigator to self.
Server and Client RPC Server RPC is called on the client an executed on the server.
Client RPC is called on the server and executed on the client. Multicast RPCs are designed to be called from the server, and then executed on the server as well as all currently connected clients.
Problem with Multicast over repnotify is that Multicast happens in game. So if a player join later, no adjustments are made.
Actor Relevancy and Priority Works with NetMulticast function

Blueprint nodes

Is Server or Switch on Has Authority Does not work with dedicated server, because dedicated has no screen?
Is Locally Controlled, Could be used to not receive a multicast.
Get Remote Role enum ENetRole ROLE_None, ROLE_SimulatedProxy, ROLE_AutonomousProxy, ROLE_Authority, ROLE_MAX,
Property Specifiers Transient : Property is transient, meaning it will not be saved or loaded
Get Instigator (aanstichter)
Get Instigator Controller
When building a custom event at graph replicates, you can choose where the function will run
RPCs (Remote Procedure Calls) Are functions that are called locally, but executed remotely on another machine (separate from the calling machine).RPC functions can be very useful and allow either the client or the server to send messages to each other over a network connection. By default, RPCs are unreliable. To ensure that an RPC call is executed on the remote machine, you can specify the Reliable keyword:
With a reliable function, it will keep sending messages to the remote until it gets conformation that the message is received. Caveat is that when nu conformation is received, the buffer overflows and the connection will get lost.
When unreliable? Particle effects, sounds , movement (goes per tick)
Kick players from the system by deleting the player controller
Player controller is replicated out off the box. Only exits on client and server. Direct communication between 2 player controllers on different clients is not possible

Main resources:

Documentation Gameinstance

Doc Display text on screen

How to find my IP