Qt Multiplayer Demo

A minimal real-time multiplayer demo built with Qt 6.8 WebAssembly and Cloudflare Durable Objects.

Any connected user clicks a button — the counter increments for everyone instantly.

▶ Live Demo · Project Plan

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How it works

Browser (Qt WASM)  ──WebSocket──▶  Cloudflare Worker
                                        │
                                   Durable Object
                                   (single global room)
                                        │
                   ◀──broadcast──  all connected clients

• The client is a Qt Quick app compiled to WebAssembly. It connects via WebSocket and sends { "type": "increment" } when the button is clicked.
• The server is a Cloudflare Durable Object that holds the counter in persistent storage and broadcasts the new value to every connected client.
• Opening the demo in multiple tabs or on multiple devices shares the same counter in real time.

Stack

Part	Technology
Client	Qt 6.8.3, Qt Quick, Qt WebSockets, WebAssembly (single-threaded)
Server	Cloudflare Workers, Durable Objects, WebSocket Hibernation API
Hosting	GitHub Pages (client), Cloudflare (server)

Repository structure

qtMultiplayerDemo/
├── client/                  Qt Quick application
│   ├── CMakeLists.txt
│   ├── main.cpp
│   ├── main.qml
│   ├── CounterClient.h/.cpp
│   └── build/
│       └── WebAssembly_Qt_6_8_3_single_threaded-Release/   ← served by GitHub Pages
├── server/                  Cloudflare Worker
│   ├── src/index.ts
│   ├── wrangler.toml
│   └── package.json
├── index.html               GitHub Pages entry point (redirects to WASM build)
└── PLAN.md                  Full project plan and progress log

Running locally

Server

cd server
npm install
npx wrangler dev   # starts on ws://localhost:8787

Client — open client/ in Qt Creator, switch to the Desktop kit and build. The desktop build points to ws://localhost:8787 by default.

Deploying

Server

cd server
npx wrangler deploy

Client — build the WebAssembly_Qt_6_8_3_single_threaded-Release target in Qt Creator, then commit the five output files (*.html, *.js, *.wasm, qtloader.js, qtlogo.svg) and push. GitHub Pages serves them automatically.