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Upgrade Guide from MLAPI 0.1.0 to Netcode for GameObjects 1.0.0

This guide is a simple recipe to upgrade from MLAPI 0.1.0 to Netcode for GameObjects (Netcode) 1.0.0. This document will help you kickstart your upgrade process. It may not fix everything, but it should guide you in the overall process.

General overview of the upgrade process#

There are five main steps in the upgrade process.

  1. Install the new package
  2. Changes in the naming
  3. Changes in the API
  4. Changes in behaviour

Installing the new package#

This step is the easiest one. First, uninstall the old MLAPI package. For that, go to your package manager (Windows -> Package Manager) and uninstall MLAPI. After that, still in the package manager, install the package: com.unity.netcode.gameobjects. You now have plenty of compilation errors since there are quite some changes between the two libraries. Installing the Netcode package will also install three other packages :

  • Unity Transport : the low-level transport layer recommended for Netcode
  • Netcode adapter for UTP: the Netcode adapter created by Unity for Unity Transport
  • Burst: a requirement for Unity Transport

You must note that the Burst package requires an Editor restart. So restart your Unity after the installation. Unity will ask you to enter Fail Safe mode at the next boot, which is normal behaviour since all your network code is not compiling anymore.

Unity also recommends installing the multiplayer tools package: com.unity.multiplayer.tools. This package will enable the Unity profiler to understand the NetCode library and add counters for network traffic.

Changes in the naming#

Unity renamed MLAPI into Netcode for GameObjects. This renaming has an impact on library and namespace naming. First, go to all your ASMDEF files referencing MLAPI and change the reference for Unity.Netcode.Runtime. Next, you can upgrade your using namespaces using namespace MLAPI to using namespace Unity.NetCode. Change this namespace in code to if you are not using using syntax.

Changes in the API#

Unity Multiplayer Teams tried to keep most of the MLAPI intact in Netcode. However, a successful compilation still requires some changes.

NetworkVariable changes#

NetworkVariable type is now generic only and the type specified in the generic needs to be a value type. First, change all your NetworVariable* types for their generic counterpart. For example, NetworkVariableInt becomes NetworkVariable<int>, NetworkVariableFloat becomes NetworkVariable<float> and so on. Now, some of your types (string, for example) will not match the new type requirements for NetworkVariable<T>. If your type is a string, you can use FixedString32Bytes instead. One should note that this type does not allow you to change the size of the string. For custom structs that only contain value types, you can implement INetworkSerializable, and it will work. Finally, for the other types, you will need to create your own NetworkVariable. To achieve that, create a new class, inherit from NetworkVariableBase, and implement all the abstract members. If you already had custom NetworkVariable, read and write functions now uses our FastBuffer to read or write from and to the stream.

Scene Management changes#

The scene management had some changes unifying the way users uses it. First, it is now under the NetworkManager Singleton. Consequently, you directly access it like so :

var sceneManager = NetworkManager.Singleton.SceneManager;

Next, there is now only one scene event instead of many: OnSceneEvent. You can subscribe to it and get scene events information from the SceneEvent class. In this class, you will find the SceneEventType, which will give you precisions on what type of event is coming from the Scene Manager. Finally, the primary function to switch between scenes has changed to match the Unity Scene Manager. Instead of SwitchScene, you now call LoadScene with two parameters: the scene name and the LoadSceneMode, which is the standard way to load a scene in Unity.

NetworkBehavior changes#

There are two main changes in NetworkBehavior. First, the NetworkStart method becomes OnNetworkSpawn, and we introduced OnNetworkDespawn to keep things symmetrical. Second, OnDestroy now needs to be overridden since NetworkBehavior already uses it.

Changes in behaviour#

We tried to keep the behaviour changes minimal put two changes may cause errors in your scripts. First, the NetworkManager now does its connection shut down when the application quits. If you were doing it by yourself, you would end up with an error saying that you tried to disconnect twice. Second, the library now fires all the OnValueChanged events from the NetworkVariable after the OnNetworkSpawn (previously known as NetworkStart) method has returned. You will need to refactor any scripts depending on this order accordingly.

Next Steps#

For instructions on how to install Netcode for GameObjects please see here