Delay-based netcode using steamworks

[overdyers]

Might be completely out of scope but online co-op would be nice and all you'd theoretically have to synchronize is the save file, inputs and random determinism, I do not know hades, it could be an absolute nightmare to get the game to act in the described way but i've implemented delay based netcode in other projects before and its pretty easy to work with.

A nice proof of concept would be the training area working.

If you aren't very knowledgeable of delay based netcode:

• You'd have make the games core update logic a fixed timestep system.
• The game would capture your inputs, send it over the network with the attached frame id and input data, while storing the input data in an dictionary / array with the corresponding key (frame id + delay), and whenever the game reaches that frame id, it uses the input data from that dictionary.
• Prevent the game from updating if the frame id was to exceed a remotes last synchronized frame id.
• Prevent "Deadlocking" which is where you and a remote are on the same frame id, causing neither clients to progress, its pretty simple, just continue capturing and sending inputs even if the game isnt progressing.
• Ping pong packet
• Make delay manually configurable

Optional Quality of Life:

• Calculate ping and display it above players heads,
• Automatically set the amount of delay to the highest ping out of all remotes, rounding to ceiling (HighestRemotePing / FixedFrameRate)

I do not know C++ so I cannot really help with the C++ side.
I have done Lua for about 5 years though.

Provided C# code examples
https://github.com/nptnk/TSBRaylib/blob/main/TSB/src/Engine/Handlers/UpdateHandler.cs
https://github.com/nptnk/TSBRaylib/blob/main/TSB/src/Engine/Networking/DelayNetcodeImplement.cs
https://github.com/nptnk/TSBRaylib/blob/main/TSB/src/Game/Input/InputValue.cs
https://github.com/nptnk/TSBRaylib/blob/main/TSB/src/Engine/Input/TickBasedInput.cs

[TheNormalnij]

Hi. Thank you for your interest in the project!

There is one big problem - the game logic is not based on ticks. Hades 1 and Hades 2 use coroutines (green threads) and triggers inside functions to handle logic.

Technically, it should be possible to sync animations. inputs, and some key events. Player 1 (host) handles the game logic and the second player moves his character only.

I'll try to do that for Hades 2 first

[overdyers]

Ah yes delay based would be very hard to implement under those circumstances, a basic lockstep implementation might be good for that then, league of legends does it nicely.