Can you do multiplayer in Unity?

Yes, you can create multiplayer games in Unity. Unity provides built-in support for networking through the Unity Multiplayer Service and the Unity Netcode for GameObjects package.

How does multiplayer work in Unity?

There are two main ways to implement multiplayer in Unity:

• Unity Multiplayer Service – A cloud-based solution that handles hosting multiplayer games and managing network connectivity.
• Unity Netcode for GameObjects – An open source networking framework that handles lower level networking logic like serialization and connection management.

The Unity Multiplayer Service is the easiest way to get started with multiplayer. It handles hosting games on Unity’s servers, managing network connections between players, and synchronizing game state. This allows you to focus on the gameplay and user experience rather than complex networking code.

Unity Netcode for GameObjects gives you more control over the networking implementation. You host games yourself and implement the networking logic in your game code. This allows for more customization but requires more networking expertise.

Both options use the high-level Networking API in Unity for managing network objects and connections. This provides a unified development experience no matter which networking approach you use.

How to implement multiplayer with Unity Multiplayer Service

Here are the basic steps to implement multiplayer with Unity Multiplayer Service:

1. Import the Multiplayer Networking package into your project.
2. Configure your project for multiplayer in the Multiplayer service page in the Services window.
3. Create a Network Manager object which orchestrates the networking.
4. Create network prefabs for your game objects that need to be networked.
5. Spawn and control network objects from client and server scripts.
6. Connect client builds to the multiplayer service to join game sessions.

The Multiplayer Service handles hosting the game server, managing network latency and quality, NAT punchthrough, and connecting players together into game sessions. You can focus on the gameplay logic and synchronizing game state.

Some key advantages of using Unity Multiplayer Service:

• Fast and easy setup – Get started quickly without needing to write complex networking code.
• Multiplatform support – Games work across desktop, mobile, console, and VR platforms.
• Scalability – Games can scale to support large numbers of concurrent players.
• Matchmaking – Automatic matchmaking system can match players based on skill or location.
• Authentication – Player authentication with Unity accounts built-in.

Implementing a simple multiplayer game

Here is an overview of implementing a simple multiplayer game with the Unity Multiplayer Service:

1. Create player prefab with Network Identity – This enables it to be spawned over the network.
2. Create Network Manager object – This will bootstrap the networking and connect to the service.
3. Create scripts to control player movement and actions on client and synchronize state on server.
4. Build client – Standalone, mobile, etc. Connects to service to join game sessions.
5. Handle player joining/leaving sessions and spawning player prefabs on connect.
6. Use NetworkTransform to synchronize position, Remote Actions to call methods, etc.

The Multiplayer Service handles the hosting and networking complexity behind the scenes. You can focus on the client-side controls and server-side game state management.

How to implement multiplayer with Unity Netcode for GameObjects

Here are the basics of implementing multiplayer networking directly with Netcode for GameObjects:

1. Import Netcode for GameObjects package into your project.
2. Create scripts that inherit NetworkBehaviour – these have networking logic built-in.
3. Implement server and client Netcode handlers in scripts such as OnServerStart, OnClientConnected, etc.
4. Spawn networked game objects from server using NetworkManager.
5. Synchronize state using NetworkVariable synchronization.
6. Host relay server standalone or in cloud to connect clients.

With Netcode you have full control over the networking implementation. You can optimize and tweak as needed for your specific game.

Some benefits of using Netcode for GameObjects:

• Lower latency than Multiplayer Service – you can tune for fast-paced games.
• In-depth networking statistics and debugging tools.
• Fully customizable – modify network model to suit your game.
• Authoritative server support – full control over cheat prevention.
• Dedicated game servers – can scale to large player counts.

Implementing a simple multiplayer game

Here is an overview of using Netcode to add multiplayer:

1. Create scripts for player, weapon, etc. that inherit NetworkBehaviour.
2. Implement OnServerAddPlayer to spawn player prefab when connected.
3. Register server and client RPC functions to synchronize state.
4. Spawn enemies and projectiles as NetworkObjects from server.
5. Use NetworkVariable to sync data like health, score, etc.
6. Host relay server on machine or cloud platform.
7. Handle client connect/disconnect events.
8. Make sure to validate actions on server for security.

With Netcode you have more control and responsibility over the networking implementation. But this allows for optimization and full control for your game’s needs.

Which multiplayer option should you choose?

Choosing between the Unity Multiplayer Service and Netcode for GameObjects depends on your game, team size, and level of experience.

Some guidelines on which to use:

Multiplayer Service	Netcode
– Simple multiplayer needs	– Need very fast networking / low latency
– Small team or solo developer	– Have networking / backend experience
– Quick development time important	– Require high customization / control
– Mobile or console game	– Building MMO or Battle Royale game
– Don’t want to manage servers	– Plan to host dedicated game servers

For many teams, starting with the Multiplayer Service makes sense to prototype and iterate quickly. Later on Netcode can be added if more control or optimization is needed.

Multiplayer Service pros

• Fast development time – Get started quickly
• Easy to use – Less networking experience required
• Scalable hosting – Handles large player counts
• Built-in services – Matchmaking, lobbies, voice chat
• Cross platform – Support mobile, console, desktop, and VR

Netcode pros

• Very low latency – Tuned for fast paced real-time games
• Authoritative server – Extra cheat prevention
• Full control – Customize and tweak networking model
• Own dedicated servers – Scale massively with standalone backends
• In-depth metrics – Network profiling and debugging

When to choose each

Use Multiplayer Service if you want:

• A fast, easy solution without managing servers
• Shared and hosted infrastructure
• Quick prototyping and iteration
• Cross platform support

Use Netcode if you need:

• Very low latency deterministic networking
• Fully authoritative servers
• Deep networking statistics and debugging
• Ability to scale massively with custom server backends
• Optimization and customization of networking model

For many teams starting out, Unity’s Multiplayer Service is the best place to start. It’s easy to implement and takes care of the hosting complexities. Later on you can integrate Netcode as needed if you outgrow the Multiplayer Service capabilities.

How to choose a multiplayer architecture

When implementing multiplayer, you need to decide on an overall architecture. The architecture will depend on the type of game and number of players.

Here are some popular architectures:

• Peer to peer – Each client connects directly to each other. Good for games with fewer players like 4-8.
• Client-server – Clients connect to a centralized server. Simple and scales well to 100s of players.
• Authoritative server – Server validates all client actions for cheating. Essential for competitive games.
• Dedicated servers – Standalone server processes for each game session. Required for MMOs and large player counts.
• Cloud hosting – Host dedicated servers on cloud platform like AWS or Azure. Provides scalability.

For small scale games, a basic client-server architecture is a good starting point. Use the Multiplayer Service to host the server and validate actions on the server for security.

For large scale games with 100+ players, you will need to look at authoritative servers, dedicated backends per game session, and cloud hosting for scaling.

Key questions for choosing architecture:

• How many concurrent players?
• How much bandwidth per player?
• How much latency can you tolerate?
• iOS / Android support needed?
• Peer to peer or client-server?
• Authoritative server or distributed trust?

Answering those questions will help guide the architecture choice. Be sure to allocate enough time to design and iterate on the architecture before full production.

Best practices for developing multiplayer games

Here are some key best practices when developing multiplayer games in Unity:

Use prefabs and object pooling

Reuse networked prefabs and leverage object pooling for better performance. Avoid instantiating objects at runtime.

Use interpolation and prediction

Smooth out perceived latency by predicting player moves locally and interpolating positions. Don’t just snap objects to latest received position.

Implement client-side prediction

Allow players to move locally without waiting for server confirmation for a more responsive feel. Validate on server later.

Authoritative server logic

Don’t trust the client! Validate health, damage, scores etc on the server to prevent exploits.

Optimized data synchronization

Only sync data needed by clients. Use delta compression rather than sending complete game state.

Handle latency, packets loss

Implement interpolation, prediction, lag compensation, and other techniques to account for lag.

Secure your game traffic

Encrypt traffic and implement anti-cheat measures. Don’t trust client data.

Test with real players early

Do in-house playtests starting early in development to find multiplayer issues.

Monitor server and network metrics

Track stats like CCU, bandwidth, latency to optimize and plan server capacity.

Following multiplayer best practices will lead to more robust, smoother games with fewer glitches and a better player experience.

Conclusion

Implementing multiplayer in Unity is straightforward using the built-in networking solutions. Both the Multiplayer Service and Netcode for GameObjects allow you to create networked games across multiple platforms.

The Multiplayer Service provides an easier starting point while Netcode offers more customization for developers wanting more control. Make sure to design the networking architecture and infrastructure to fit the scale and performance needs of your game.

Leveraging Unity’s tools and following best practices for optimizing synchronization, handling latency, and securing data will lead to high quality multiplayer game experiences.