Networking and Replication

Unity networking habits do not transfer directly to Unreal. Unreal has a built-in authority and replication model that shapes how gameplay code is written.

Authority Model

Unity Version

In Unity, networking choices vary a lot depending on the package or third-party solution.

Unreal Version

In Unreal, the server is usually authoritative for important gameplay state.

Key Difference

You often write code with explicit server, client, and owning-client responsibilities in mind.

Server and Client Roles

Concept	Meaning
Authority	The machine that owns the true gameplay state, usually the server.
Autonomous proxy	A client-controlled pawn on its owning client.
Simulated proxy	A replicated actor viewed on other clients.

`HasAuthority`

Use HasAuthority() to check whether an Actor is currently authoritative.

if (HasAuthority())
{
    SpawnLoot();
}

This does not mean "am I the server?" in every abstract sense, but it is a common gameplay check on replicated actors.

Replicated Properties

UPROPERTY(Replicated)
int32 CurrentAmmo = 30;

Replicated properties must also be registered in GetLifetimeReplicatedProps.

RPCs

Unreal supports remote procedure calls with UFUNCTION specifiers.

Server RPC

UFUNCTION(Server, Reliable)
void ServerFireWeapon();

Client RPC

UFUNCTION(Client, Reliable)
void ClientShowHitMarker();

NetMulticast RPC

UFUNCTION(NetMulticast, Unreliable)
void MulticastPlayImpactEffect();

Reliable vs Unreliable

Reliable should arrive, but use it carefully
Unreliable is fine for frequent cosmetic updates where occasional loss is acceptable

Replicated Gameplay Classes

Class	Typical Network Role
`GameMode`	Server only
`GameState`	Replicated shared match state
`PlayerController`	Exists on server and owning client
`PlayerState`	Replicated per-player data
`Pawn` / `Character`	Often replicated gameplay avatar

Common Mistake

A common trap is trying to drive all gameplay from local client scripts, then expecting replication to "just sync it later". In Unreal, important state changes usually need a server-authoritative path from the start.