Building a multiplayer game server in Go and Webassembly - Arne Wieding - Delivery Hero

The talk discusses the functionalities of Triebwerk, an experimental Go multiplayer game server that I have developed for the browser game http://panzerkampf.io, which is a side project of mine (still in development). Video of the game and multiplayer techniques used: https://www.youtube.com/watch?v=TC6hluQ8UjY

The talk details the implementation of the server in Golang. To achieve that It first illustrates the basics of multiplayer game development in regards to networking and latency compensation techniques. It then briefly goes over the overall architecture of the game server and the algorithms for player movement, collision and hit detection and their implementation in Go
In addition, the talk details how to reuse the core game logic written in Go as a Webassembly module in the Javascript client of the game, using the latest WebAssembly features of Go v1.13. The usage of WebAssembly enables the use of the same code on the server and on the client, which allows Go to replace Node.Js for similar use cases.

Transcript

1. Building a multiplayer game server in Go and Webassembly by Arne Wieding https://twitter.com/awdng https://github.com/awdng
2. whoami && whatisthis Arne is: • A Software Engineer at Delivery Hero • The angry German • Not a professional Game-Developer The project: • Called Panzr.io • Just a side-project and very much a prototype • The server is open-source • You probably should not use it (in production)
3. Introducing panzr.io
4. Introducing Panzr.io • A game based on open-source technologies • Using the web as a distribution platform • Lightweight and fast • Exploring fundamental multiplayer techniques • Extend Go knowledge
5. Panzr.io Architecture Client Application Three.js Firebase Game Component Web browser Javascript Environment WebGL Vue.js Golang runtime Game Component Gorilla Websocket Game Logic WebAssembly Module Websocket over TCP/IP Server Application Websocket
6. Panzr.io Deployment Caching Play via Websocket Amazon S3 Game Client Web browser API Server Cloudflare Dedicated Server Game Server Docker Container Game Server Docker Container Update Game State via GRPC Player / Game data via REST using GRPC Gateway
7. Introducing Triebwerk https://github.com/awdng/triebwerk Status: • Multiplayer server Triebwerk is Open-Source • Written in Go (obviously) • Just a prototype • Fork it to port it to your game • Feedback/Contributions welcome!
8. How do games actually work? Process Input Update Game world Render Game world 60 FPS = ~16.67ms per Update The game loop
9. Server Authoritative Architecture • Communication only through the server • Clients send all their input to the server • Server has the authority over the simulation • Prevents cheating but introduces latency
10. Client side prediction and server reconciliation • First popularised by QuakeWorld • Simulate movement locally • Constantly sync with the server state • Correct local state based on server state
11. Client interpolation • Network Updates < Frames per Second • Interpolation between past states • Conservative algorithm • No extrapolation
12. Defining boundaries Limitations: • all game logic only in 2D Space • Even surfaces • Input control via keyboard only • Limited map size • Slow-moving vehicles • No physics engine
13. Server implementation Game Loop Protocol Websocket Transport GameState Collider Info Controls (0..n) Player Map Weapons NetworkManager Clients Encoding / Decoding Sending / Receiving Receiving Input Broadcasting State Updating State
14. Player Movement
15. Collision detection
16. Binary Data Transfer • Minimises the resource usage • Prevent packet segmentation • Minimises effects of packet loss
17. • Filesize > 2MB • Server and client compute the state based on the same logic • Data transfer through binary types WebAssembly Module Game logic Server → Client
18. WebAssembly Module Encoding the state in Go Decoding the state in Javascript
19. Wrapping up Results and Learnings • Playable prototype • Isomorphic apps using WebAssembly • Multiplayer server with low resource usage • Based entirely on Open Source • It's fun! What else? • Triebwerk clean-up • Releasing Panzr.io • Article series on implementation details • https://github.com/awdng/triebwerk • Please do whatever you want with it https://twitter.com/awdng https://github.com/awdng
20. Enough talking, let's play! http://panzr.io/#s/4p78p
21. Thank you! https://twitter.com/awdng https://github.com/awdng