UE4 Networking Development Tips

For more detail, you can visit Networking and Multiplayer. In this blog, I just share brief introduction and some tips in development.

1 Actor Role

For UE4 network project, Dedicated Server and Client are running same copy of codes. Programmer can use below roles to distinguish actors：

ROLE_SimulatedProxy：Locally simulated proxy of this actor.
ROLE_AutonomousProxy：Locally autonomous proxy of this actor.
ROLE_Authority：Authoritative control over the actor.
Tips: Notice that actors with ROLE_Authority are running at the dedicated server for network project.

2 RPC

Called on server and execute in client：

  UFUNCTION( Client );
  void ClientRPCFunction();

Called on client and execute in server：

  UFUNCTION( Server );
  void ServerRPCFunction();

Called on server and execute in all clients：

  UFUNCTION( NetMulticast );
  void MulticastRPCFunction();

Implementation of RPC function

  void SomeRPCFunction_Implementation()
  {
  }

Validation and Reliability

Using keyword Reliable or UnReliable to determine the rpc is called on a reliable or unreliable channel. Using keyword WithValidation to assign validation function：

  UFUNCTION( Server, Reliable, WithValidation );
  void SomeRPCFunction( int32 AddHealth );
	
  bool SomeRPCFunction_Validate( int32 AddHealth )
  {
     return true;                             
  }

Tips: Notice that if the validation function return false, the caller will be disconnected.
Tips: No all actor can call RPC function, only those actors directly or indirectly controlled (owned) by PlayerController can call RPC function effectively.
Tips: RPC function drived by UNetDriver::InternalProcessRemoteFunction.

3 Replication

Actor or ActorComponent : Controlled by property bReplicates or function SetIsReplicated

Properties: Using keyword Replicated in C++ and replicated properties should be add to GetLifetimeReplicatedProps;

  class ENGINE_API AActor : public UObject
  {
      UPROPERTY( replicated )
      AActor * Owner;
  };
	
  void AActor::GetLifetimeReplicatedProps( TArray< FLifetimeProperty > & OutLifetimeProps ) const
  {
      DOREPLIFETIME( AActor, Owner );
  }

Tips: Order to call RepNotify function and RPC function cannot be promised.

4 Reconnection

UE4 build-in networking is not supporting reconnection mechanism. Developers should achieve two type of reconnections.

Reconnection for killing client process: relogin dedicated server again for all game logic.
Reconnection for heartbeat timeout: refresh all game logic when reconnected.

References

[1] Networking and Multiplayer

Tags: UE4 Network Vistied: