Question How to deal with trigger input and lagging clients?

I'm back at looking at my side project agian. And I delved into trying to solve my issue with clicking a button to enter a "controlling" state, where the player would enter and leave with one press of button.

With some logging done, it seems that when the player laggs my code will not create commands for every server tick, which leads to the server to copy the command for the missing ticks - introducing more trigger input. (Is this a correct observation?)

My InputSystem is running in the GhostInputSystemGroup, and only adding a command for the
ClientSimulationSystemGroup.ServerTick.

My question then is, what would be the proper way to solve this?
My current thought is to store an extra field of the generated tick & require a match for the executing tick to deal with trigger logic.

 

Thank you! That sounds like a good direction. This would solve losing a packet even outside of the bufferd commands to the server compared to what I was suggesting. I was also thinking along the lines of sending the tick of the trigger, which could work similarly and you could use the knowledge of what tick it should have been triggered at, but with a counter you could also do logic around how many times it was pressed to either consume or modulus the value ^^. Not sure if either of these additional features will be useful to me though. Thank you!

 

Is possible to just use RPC? This solution seems complicated.

 

I noticed when I rewrote my FPS camera rotation from sending the full state in the command to using deltas that a tangential issue arises when lagging. Since it seems to duplicating commands on server and use last on client, it will use deltas multiple times boosting the rotation when lagging both for predicting and server which feels weird. Right now the only solution I have for this is to add a "Generated tick" field to check vs the tick fetched and clear any deltas if they don't match. Would there be a better approach here?

 

I would like to confirm this with u. At 1.0 release does it means it will have reliable events feature and then RPC feature will be completely removed or it will stay there?

 

Actually wat's the use case for RPC? Currently I just use it to like send select hero RPC from client to tell server which hero to choose and also upgrade hero level and upgrade hero skill level RPCs from client to server

 

Code (csharp):

1.  
2. [UpdateInGroup(typeof(GhostPredictionSystemGroup))]
3. class ProcessInputSystem : SystemBase
4. {
5.  public void OnUpdate()
6.  {
7.     ...
8.     inputBuffer.GetDataAtTick(currentTick, out var currentInput);
9.     var prevTick = currentTick - 1;
10.     if(prevTick == 0)  --prevTick;
11.     inputBuffer.GetDataAtTick(prevSampledTick, out var prevInput);
12.     if((currentInput.ButtonPressed - prevInput.ButtonPressed) > 0)
13.     {
14.             //Process the button pressed
15.     }
16.  }
17. }
18.  

I do not fully understand line 10 of this code. Is this a typo? If the prevTick happens to equal 0, then make it equal -1?
Were you meaning to make sure prevTick would never end up negative?

Also, I implemented this today (except for line 10) and it works great in the editor. But for some reason in my builds, some of my inputs are being "eaten" and never firing. It's very inconsistent. I am not sure why, will require more investigation on my part.

 

I have a project here where I implemented the above suggestion of

However, it is producing some odd results for me.

I made this project modeled after how Rival has their online FPS example set up. How they handle inputs is like this:

1.

OnlineCharacterCommandsSystem.cs

(only runs on Client)
Takes inputs on Client and puts them into a

ICommand 

struct and uses

AddCommand 

to put it into a buffer. This is where I do the incrementing of "you pressed jump" into a variable called

byte JumpRequested

.

2. Ghost Authoring Component has "Support Auto Command Target" checked in Inspector, so Commands are sent to Server.

3.

OnlinePlayerControlSystem.cs

(runs on both Client and Server)
Reads the

ICommandBuffer

, gets the

ICommand 

buffer at a tick and a previous tick, and performs the subtraction (as suggested). If the

tick - prevTick > 0

, then sets the

bool 

value of Jump to true.

4.

OnlineCharacterSystem.cs

(runs on both Client and Server)
Loops through all Entities that have the

OnlineCharacterInputs 

struct. If any of those have a Jump value set to true, then the character (a cube) moves up 1 meter on the y-axis.

However, when I make a build of the project on my machine, I get many inconsistent instances where the Server never seems to receive the command. Here is a set of simple Debug.Log statements I have.

The first block here, is what the Debug.Logs look like on a failure.

Code (csharp):

1. Client: Jump Pressed 1 times at frame: 398. Added to buffer at tick 152
2. Client Jumped. Tick: 152 Frame:398
3. Client: Character Jumped. Frame:398

What ends up happening is that the Client makes a very short attempt to jump, but then the Server corrects it and a jump never occurs.

Essentially what it looks like to me, is that the Server never receives an

ICommand 

at tick 152 that has

JumpRequested 

with a value of 1. Instead it receives one that has

JumpRequested 

with a value of 0.

And here is what the Debug.Logs look like on a success.

Code (csharp):

1. Client: Jump Pressed 1 times at frame: 993. Added to buffer at tick 476
2. Client Jumped. Tick: 476 Frame:993
3. Client: Character Jumped. Frame:993
4. Client Jumped. Tick: 476 Frame:994
5. Client Jumped. Tick: 476 Frame:995
6. Client Jumped. Tick: 476 Frame:997
7. Server Jumped. Tick: 476 Frame:998
8. Server: Character Jumped. Frame:998

This causes a successful jump, however I'm not a big fan of how Jump ends up being true for 5 frames. But this is not yet a problem for me that I want to address.

I would really, really appreciate it if someone could take a look at this project and see if this is a problem with my implementation, is a Unity bug, or if it even happens on your machine. I am attaching a zip of the project files.

This uses Unity 2020.3.34f1.

To build it, go to the

BuildConfig 

folder, highlight

OnlineClientServerBuildConfig

, press

Build 

in the top-right of the Inspector.

All you need to do to run the build is press the Host button on the main menu screen. This will create a server and connect to it as a client.

In order to see the Debug.Logs, I find the best way is to go into Powershell and paste this in there after running the build.

Code (csharp):

1. Get-Content "$($env:LOCALAPPDATA)\..\LocalLow\tylo\NetCodeProblem_ClientServer\Player.log" -Wait

 

Hello Phil, thanks for the answer. Your suggestion did work! No more mysterious Ticks that contain a value of 0.

However it does leave me with one lingering question. If I never reset to 0, then how can I get away with using a

byte

as my value type for

JumpRequest

?

My first thought was to write some kind of "wrap around" logic to reset it to 0 once I get near 255. But if you can think of an easier way, I am all ears.