Feedback My experience with netcode for GameObjects thus far

Background
I'm a developer for about 7-8 years. I got a bachelor degree in IT. My study was called "Game Technology and Production". Most of my experience is in XR and UGUI due to my daily job.
So as a challenge I started development of a hobby project. A multiplayer Tower Defense game using Netcode for GameObjects. I have no experience with other multiplayer API such as Mirror. So I wouldn't be able to compare them in terms of ease of use.


The network manager
The singleton pattern. Everytime you want to access anything you have to write

NetworkManager.Singleton

Want to access the NetworkSceneManager?

NetworkManager.Singleton.SceneManager.LoadScene

It would've been easier if the

NetworkManager

was a static class and the configuration of it in the inspector as a component that communicates with the static

NetworkManager

class.
That way you can write

NetworkManager.StartServer()

NetworkSceneManager.LoadScene

just like many other Unity based API.
If you need the MonoBehaviour lifetime of Unity that could be done in a proxy component instantiated at the start of the server.


Switching scenes
I've setup a Main Menu and Lobby UI using UI Toolkit. Selecting multiplayer and a submenu 'Host' I start the NetworkManager server and switch the scene to the Lobby Scene.
Upon entering the Lobby scene, I have a lobby controller that keeps track of the connected clients and their ready status. For every client connected I need to sync up their username, ready status and character / race in the UI. So I called a server rpc from the client to add themselves to the connected list with their username and last preferred character / race. I got an error telling me that the RPC was called on a NetworkObject that is not in the spawned object list. After quite some time debugging why, I found out that I switched the scene the regular way using Unity's SceneManager and not the NetworkSceneManager.

It would've been nice if I had a warning / error message that I changed scenes with the regular API.
Or it would've been even better if you can use the regular SceneManager API.
There is a

SceneManagerAPI.overrideAPI

perhaps you can hook in the required functionality through that. So you wouldn't need to call

LoadScene

through the

NetworkManager.Singleton.SceneManager

.


Documentation
Some pages are already out of date. Like the NetworkVariables still mentions NetworkDictionary which has been removed in 1.0.0.


Missing Features
A lobby controller component with connection UnityEvents and a client ready UnityEvent.
It would make prototyping a lot faster that handles these.
ClientConnected, ClientDisconnected, ClientLostConnection, ClientReconnected, ClientReady

Addressables support, this is something I've already mentioned in another thread. It's on the roadmap.
Having a list of prefabs on a NetworkManager loads them all into memory even when you don't use them.
In my case if I were to have 20 different towers per race and have 4-5 different races. That'd mean I have to load 80-100 towers into memory at all times. Even though one of those races may not be chosen or a large selection of towers would not be available. But they're still being loaded into memory at the Bootstrap scene.
Addressables in this case would be nice to load in the prefab only when it is required.


Unclear
Ways of referencing choices made by the player. Choosing a character, choosing a tower. In single player I'd have a scriptable object with a list of player selected towers as AssetReference. Instantiate them when selected through the UI.
In multiplayer I somehow need to synchronize the selection into a List. Which is something I can't wrap my head around how since you can't reference prefabs.
I have looked at the Boss room example but that project feels like a code spaghetti to me. Finding a needle in a haystack. Which is why I looked at the bitesize examples but that case doesn't seem to be in there. It does have a lobby but no client based selections.


I'm learning slowly but I could use some more bitesize examples on how to mess around with data and references. I find 'to the point' examples easier to follow than the boss room project.
The post turned more into a bit of a rant but I really want to try to create a multiplayer game with it.
I just need to learn more before I can really use it to create a game with it.

 

I'm working on a lobby, it's a little different to what you're after as it's a lobby with multiple rooms but follows the same principles. Here's an over-simplified version of part of the workflow taking rooms out of the equation:

• On client side
  • Client enters lobby
• On server side
  • Create new player
  • Add player to lobby
  • Spawn new player
• On client side
  • On each player network spawn
    • Display player details in UI
• On client UI selection (character, tower, ready)
  • RPC selection to server
  • Server updates player selection (NetworkVariable)
  • Selection propagates to all players in lobby

The lobby keeps a list of all the players. I do also spawn the lobby as well but I've removed functionality from it so it's not doing so much right now, but I have the players as children of it as it's easy to see who's in it.

I had a conversation with one of Unity's product managers and one of the things I mentioned was having more small real world examples. It's good to have the Boss Room example but it's a bit overwhelming for the uninitiated.

That page has been updated but it's under the develop tab for some reason.

 

Bitesize samples could be as simple as several different scenes doing different things.

Setting up the network manager to host and load the game scene.
To get familiar with starting the network manager and getting from a menu screen to a game scene.

Have a small uGUI / UI Toolkit setup where there is a float number and a button to randomize this number.
You get to learn how to do a ServerRpc and use a NetworkVariable<float> to set a random value server side.
side note: UI Toolkit setup is a bit different because it doesn't have a GameObject hierarchy unlike uGUI.
side question: Can a NetworkVariable be on a Scriptable Object instead of a GameObject with a NetworkBehaviour component containing the NetworkVariable?

You can expand on this example by making each player have their own random number and their own button to click.
You get to learn how NetworkVariable ownership works. Players can only change their own number.

Have a small uGUI / UI Toolkit setup simulating a chat window. Starting off with a input field to set your player name.
Then have a window with a ScrollView / ListView and an input field for chat input.
You get to learn how to do a ServerRpc with user input and a ClientRpc to update the client's ScrollView / ListView.

You can expand on this example by announcing that a player joined / left the chat room.
You get to learn how to disconnect as a client and to subscribe to the Client Connected / Disconnected callbacks. Though I don't know how this goes with player names. Setting them before connecting or after connecting, like a profile.
Upon connecting you can't immediately instantiate a player instance without knowing their name. Or you'd wait until you get their name and then instantiate it.

With all previous knowledge you can setup a lobby room with uGUI / UI Toolkit.
Starting the network manager as host or as client depending whether you host or join. Going from the main menu to the lobby. Upon joining you take a slot and have your profile name displayed with a ready button you can click. Upon all being ready the Start becomes available, transitioning from Lobby to Game scene.

You can expand on this example by having the player choose their character i.e. a cube, capsule or sphere.
You learn how to set a reference to a prefab that should be used as model for the player and instantiate it upon entering the game scene.

Then going from the Game Scene back to the lobby, people may change their character. Go for another round or disconnect.

In the end it is about setting scenes up, transitioning between them, connecting / disconnecting, getting data from one scene to the other, synchronizing data, changing data based on player input / choices.

Personally I use UI Toolkit, Scriptable Objects and Addressables. I'm mostly struggling with how to set references of prefabs per player. i.e. a character selection, a subset selection of tower prefabs. To set this reference server side and do a ServerRpc to instantiate that prefab with ownership for that player. But you can't reference that prefab directly in the ServerRpc method. Prefabs aren't value types whilst normally in single player you'd just reference the prefab (or AssetReference). I'd keep the list of towers in a Scriptable Object containing a List. With Netcode the workflow isn't entirely the same due to Server / Client communication.

 

I've not used it for a while but I have a test project where I tested particular aspects of Netcode by running them at a click of a button. It got pretty messy over time but a more modular approach demonstrating different aspects like connect, disconnect, network callbacks, network variables, onChange calls etc with nicely separated code that's easy to dig into would aid understanding.

While you're here there's a few issues I'd like to mention.

The Hello World videos were made pre v1 so some information on them like parts of the NetworkManager are out of date.

I've seen a few of the documentation pages have been updated under develop which leads having to check two places to find the latest version. The documentation could do with a pass putting the latest pages in the correct place and removing any remaining pre v1 references. The develop section doesn't seem to be serving much purpose at this point in time.

Some bug fixes only work with Unity transport and you wouldn't necessarily know about them unless you know where to look. This may cause some confusion while UNet remains the default transport.

It would be handy when there's a new preview release that it gets a mention in the Release Announcements thread.

 

That all sounds promising, I've barely looked at Boss Room as I prefer to see examples in isolation but it's good to know the code will be improved so it's easier to go through when I need it.

In an ideal world when looking for information and examples I'd like a workflow approaching this:

• Google search
• Link to Netcode documentation
• Description of functionality
• Code examples, use cases
• Link to practical example, where it can be found in a bitesize / Boss Room project
• Link to video (and time) where the subject is being covered.

I'm all for less effort on the user's part (ie me).

I missed this part:

I tend to only look at the release notes if a preview release breaks something, which isn't often. I mentioned it as I think major improvements or fixes should get a mention on the forums in case it's missed elsewhere. It does raise the point of are there use cases for staying with the UNet transport or is it recommended to switch over?

 

Having project samples around is certainly a good thing. It is not only for the purpose of educating others but also for validating the package itself. Can things be done easier? What can we do to improve? If you would scale up the boss room, what problems would you face? (looking at the NetworkManager's Networked Prefabs list that list would probably explode).
What are / were your biggest problems with the Boss Room project and how would you solve them?
How do you keep things modular?
Many questions can be asked as validation, improvement could be a result.

As for the Boss Room project and its size, any developer that would enter a mid or late stage of a project would be overwhelmed by all existing code and how it all hangs together. You don't know what the thoughts were of the team and how it progressed over time. You have to dive in and get to know how it all works together. It could be an entire different workflow than your own. (Which in my case it is or a mix of it.)
I didn't totally get where data was stored, changed or how/where it got synced together. I mean I used Rider to F12 my way through. Search for what accesses / changes certain fields had. Or just look in playmode what components were attached to the game objects. I would probably understand it eventually, but I would've had to spend a lot more time into it. Which I decided not to do and go for more bite sized samples to get a quicker understanding. I do occasionally have a peek at the Boss Room project though.

It would most certainly help understanding the Boss Room project as a whole or to be able to learn how you can solve the same problem in your own project. So making bite-size samples from the boss room makes sense to do. A lot of it is already there.

I'd be very much looking forward to more bite size samples and more explanation of how things work together.

 

I'd actually like Unity to take on bigger projects. Boss room is a great example of the type of tech demo Unity is great at making. Unity always struggles more and more the bigger a project gets. Unity features would benefit greatly from being developed against a "real" project with whatever team size Unity is trying to optimize for. Currently Unity works best with tiny teams, though I don't think that is the intent. Maybe?

 

I get your point, although the bigger the project the more specialized the solutions and approaches get, and one might find themselves even more lost. As for an example/educational project I believe simplicity is the way to go. A few scenes, each illustrating some feature (one lobby scene, one in-game scene where players perform some actions, one scoreboard...).

 

Honestly, even the bite-sized projects that I saw (Invaders, ClientDriven, 2DSpaceShooter) the ones mentioned in the documentation, were also equally obtuse. As someone completely new (or rather, last time I worked on multiplayer was on Unity 4.x), I didn't know where to start. Didn't know which piece of code would run first. Trying to read through the scripts, it was like, too many new concepts being introduced at the same time.

The script naming was also different from each other, one had a "BootstrapManager", another had a "MenuControl", and one had a "NetworkManagerHud". Mind you, they all do more or less the same thing (after a lot of back-and-forth checking), which is to handle starting the server/client/host. So trying to "grok" each project was like starting again from scratch, because they all name things different.

The HelloWorld and GoldenPath tutorials were the only ones useful (guess my main complaint was that they were under "Walk-Throughs" at the bottom of the Table of Contents, when I kept searching for something like "BasicTutorials" at the top or some sort of tutorials near the "Getting Started" section and couldn't see any). Ultimately I understood more from Youtube videos (Tarodev, Dilmer Valecillos) than the sample projects.

 

I have the same issue and i can't find a way to reference an object that is spawned on the server. Any advise?

 

I know i can get the id of the object but there are no functions like GetGameObjectByID(id)

 

@RikuTheFuffs-U yes, thank you

 

For a lot of items and in case all item IDs are unique (which they should be), you can also use a Dictionary instead of a List to reduce lookup times. This is because the lookup complexity of a Dictionary is O(1) and the lookup compexity of a List is O(n), which bascially means that the more items there are in a List the longer finding an item will take, while it will take the same amount of time for a Dictionary, no matter the amount of items in it.

Code (CSharp):

1. class ItemsDatabase : ScriptableObject
2. {
3.     public Dictionary<uint, Item> items;
4.  
5.     public Item GetItemByID(uint ID)
6.     {
7.         if(items.ContainsKey(ID))
8.         {
9.             return items[ID];
10.         }
11.         return null;
12.     }
13. }

The only problem here is that by default, Unity isn't able to serialize your

items

Dictionary. However, there are Assets like Odin Inspector as well as custom attribute drawers that allow you to serialize Dictionaries in order to expose and edit them in the Inspector. You could also keep storing all Items in a List and generate a Dictionary for lookups once at the start of your application, that you could use for runtime lookups.

 

I agree about the Boss Room example, it is useless to get started.

The documentantion on Netcode and the Gaming Services is also need a complete re-write.

Sometimes it's just a few paragraphs without any explaination on how to write the code.

Other examples include way too much code and do not explain how to do simple things.

One example, the documentation does not explain how to implement player names and sync them accross the network.

Another example, a new developer needs to bang his head a lot of times before he accidentally stumbles across ClientNetworkTransform and ClientNetworkAnimator. Such basic things should be included inside Netcode when you install the package in my opinion.

Third example, NetworkVariables. Why doesn't Unity start explaining how to do simple things like player health? You could combine the example with the "toggle open door" but that is not even explained either. How is ToggleServerRpc() used? Who calls it? How can I implement a health bar that way?

I know the answers now, but imagine being new to Unity and reading this wall of text: https://docs-multiplayer.unity3d.com/netcode/current/basics/networkvariable/

 

Sounds great and exactly like something that would solve these problems!

I will give it a go, thanks for the feedack.

 

Just got time to have a look @RikuTheFuffs-U

The BiteSize / ClientDrivenExample is exactly what I am talking about!

Integrating it to the ThirdPersonController template is very clever.

Great addition to the docs. Thanks and keep up the good work.