How to Implement Multiplayer Networking in Unreal Engine

Edited 14 hours ago by ExtremeHow Editorial Team

Unreal EngineMultiplayerNetworkingGame DevelopmentOnline PlayProgrammingReplicationLagClient-Server ArchitectureCoding

The Unreal Engine is a robust environment that is used extensively to create both single-player and multiplayer games. One of the most appealing features of the Unreal Engine is its ability to effectively integrate multiplayer networking systems. This guide will walk you through implementing basic multiplayer networking in the Unreal Engine, making it easier for developers to set up and manage seamless multiplayer experiences. We'll go over important concepts, settings within the Unreal Engine, and coding examples to make it clear to you the steps to take in a typical multiplayer application.

Introduction to multiplayer networking

Multiplayer networking within games allows multiple players to connect, interact, and communicate within a shared digital environment. In Unreal Engine, this is achieved through bespoke network protocols such as the client-server model, where one instance of the game is the server and the others are clients. The server manages the game logic and state, while clients send and receive updates. Managing this interaction efficiently requires a good understanding of networking principles and knowledge of how to implement them within the framework of Unreal Engine.

Key concepts in Unreal networking

Before we dive into the process, let's review some basic concepts needed to understand Unreal Engine networking:

Replica

Replication is the process of synchronizing the game state across different machines. The Unreal Engine uses replication to ensure that all clients have the same version of the game state. You can mark variables, functions, and classes for replication. Only variables marked for replication will be shared between the client and server.

Dedicated vs. listening servers

In multiplayer games, servers can be either dedicated servers or listen servers. A dedicated server is a stand-alone application that only runs the server version of the game, without any of the rendering or gameplay logic that the client has. In contrast, listen servers are hosted by the client, meaning the host acts as both the client and the server.

Setting up Unreal Engine for multiplayer

To set up Unreal Engine for multiplayer, you'll need to adjust several settings and understand how replication is defined. To make sure your project is ready for multiplayer, follow these steps:

1. Project settings

To configure your project for multiplayer, go to the Project Settings in Unreal Engine. Under Engine menu on the left panel, select Network.

• Enable binary multithreading: This ensures that both the server and each client run smoothly.
• Set maximum latency tolerance: This manages how much latency the system will tolerate before compensating.

2. Define player controllers

Player controllers serve as a bridge between the player's input device and the character. They receive keyboard or gamepad inputs and convert them into actions within the game. Define a player controller template using Blueprint or C++:

Example of controller script in C++:

#include "MyPlayerController.h"
void AMyPlayerController::SetupInputComponent() {
    Super::SetupInputComponent();
    // Bind input actions
    InputComponent->BindAction("Jump", IE_Pressed, this, &AMyPlayerController::Jump);
}
void AMyPlayerController::Jump() {
    if (ACharacter* MyCharacter = Cast(GetPawn())) {
        MyCharacter->Jump();
    }
}

3. Game modes and game states

Unreal Engine uses GameMode to set rules and control what happens during a game level. GameState represents the state of the game that can be shared between players. Configure both to better manage multiplayer flow:

• Open your gamemode file and make sure your logic is compatible with multiplayer aspects - like player limits.
• Implement relevant gamestates that need to be replicated across clients.

4. Making Classes replicable

Classes, especially actors, must be adjusted to allow replication. In Unreal's C++, you modify the class header to include the replication functionality:

UCLASS()
class MYGAME_API AMyCharacter : public ACharacter {
    GENERATED_BODY()
    public:
        AMyCharacter();
        virtual void GetLifetimeReplicatedProps(TArray& OutLifetimeProps) const override;
    protected:
        UPROPERTY(Replicated)
        int32 Health;
};

Understanding Unreal's network architecture

Classes and components

Some of the classes and components that are critical to implementing a fully functioning networking ecosystem include:

• Actor: The base class for replicable objects.
• Pawns/Characters: Represents players and non-player characters.
• PlayerState and GameState: House data about the players and the rules of the game, both replicated across the network.

Practical steps for implementing multiplayer

Step 1: Creating a multiplayer-friendly environment

Start by creating an environment where multiplayer can take place. Make sure the server and client settings align, and test with a dedicated or listen server.

Craft a level and set it up for multiplayer by adding spawn points and any shared resources the client needs.

Step 2: Implementation of function replica

For critical actions that affect the state of the game, use function replication. Functions marked with specifiers such as Server, Client or NetMulticast control how they are called over the network. Here's an example:

UFUNCTION(Server, Reliable, WithValidation)
void ServerDoAction();
bool AMyCharacter::ServerDoAction_Validate() {
    return true; // Add proper validation
}
void AMyCharacter::ServerDoAction_Implementation() {
    // Action to take on the server
    ActionOnServer();
}

Step 3: Testing and optimizing network performance

Once your multiplayer logic is in place, it's important to test its performance. Pay attention to latency, which can impact gameplay, and optimize network traffic in the following ways:

• Ensuring that only necessary data is replicated.
• Using Unreal's built-in network profiler to analyze network load.
• Adjusting tick rates to smooth out performance and prioritize important updates.

Conclusion

Implementing multiplayer networking in Unreal Engine involves setting up the network system efficiently, defining the game logic for both the client and server, and using Unreal Engine's built-in functions to ensure robust communication across the network. Whether you opt for a dedicated server or a listen server, it's important to understand how to create reliable replication flows and work within the engine's network architecture.

  Share This Article

If you find anything wrong with the article content, you can request an update