NosCore.ClientLab

A static recompilation of the NosTale client (a Delphi 7, 32-bit x86 Windows program) into portable C, built to WebAssembly so the client runs in a browser tab against a NosCore server. The goal is automated end-to-end testing of NosCore with the real client: no Windows machine, no emulator, scriptable.

No client content lives here. You bring your own client install. The tools read it from disk; everything they produce (generated C, Ghidra/IDR databases, builds, screenshots) stays in a local work folder outside git, and the dev server streams your game files to your own browser only.

What works

Against a local NosCore stack, in Chromium (Chrome or Edge 137 or later): the browser build needs WebAssembly JavaScript Promise Integration (-sJSPI in recomp/wasm/compile_all.py), which is how the game yields to the browser once per frame. Browsers without it, such as Safari 26 and earlier, cannot start it.

• login, server and channel selection, character selection, entering the world;
• walking, chat, the game windows (inventory, skills, ...), GM teleports between maps;
• Direct3D 9 rendering on WebGL2 (fixed-function texture stages, lighting, fog, texture-coordinate generation), GDI text through the browser's font engine, Miles audio through WebAudio;
• about 60 frames per second in town at 1080p on an integrated GPU.

Every one of the client's 19,436 functions is recompiled (90.4% of the code section's bytes; the rest is data the compiler keeps there: VMTs, RTTI, jump tables, strings). What is still open is listed in docs/STATUS.md.

How it works

NosCore.exe ──IDR + Ghidra──▶ function list + names (symbols/<md5>/)
            ──recomp/lift.py──▶ one C function per x86 function (registers, flags and x87 in a CPU struct)
                                 + recomp/runtime (shared helpers)
                                 + recomp/port   (Windows re-implemented: kernel32, user32, gdi32, d3d9, Winsock, Miles, ...)
            ──Emscripten──▶ nostale.wasm, run in a Web Worker; recomp/web serves the page and relays sockets

• Lifter (recomp/lift.py): recursive descent from the Ghidra function list, extended where Ghidra stops early (unresolved case dispatches, try/finally handlers, VMT-only methods). Direct calls become plain C calls; indirect ones go through a flat label table. A Unicorn-based differential tester (recomp/difftest) checks instruction semantics. A few hot client functions (the height ray and the path search) have hand-written versions in recomp/runtime/rt_game.c, used only for the client build they were written against and checked against their lifted bodies by recomp/difftest/overrides.c.
• Portable host (recomp/port): the Windows the client expects, implemented on browser primitives: WebGL2 for Direct3D 9, OffscreenCanvas for GDI text, WebAudio for Miles, SharedArrayBuffer rings for input and sockets (the game loop yields to the browser only at Present, once per frame, when it draws straight into the page's canvas).
• Native host (recomp/runtime, MSVC): the same generated C as a Windows executable, useful for debugging.

The full story, every gotcha found so far, and how to continue are in docs/STATUS.md.

Quick start

Requirements: Windows, Python 3 (pip install capstone pefile), Emscripten in C:\tools\emsdk, Ghidra 12 with Java 21 (for the first decompilation), a NosCore server, and the NosCore-patched client (NosCore.exe; symbols here are for MD5 51bbff3ec09d67c8425f88d74c6d5df5).

# 1. Recover functions and names (IDR + Ghidra), once per client build
./tools/decompile.ps1 -ClientExe "C:\Program Files (x86)\Nostale\NosCore.exe"

# 2. Lift x86 to C
python recomp\lift.py C:\tools\re\work\input\NosCore.exe C:\tools\re\work\functions.txt C:\tools\re\work\recomp\gen `
    --seeds symbols\51bbff3ec09d67c8425f88d74c6d5df5\recomp_seeds.txt

# 3. Build the browser version (about 5 minutes the first time, incremental afterwards)
python recomp\wasm\compile_all.py --web

# 4. Serve it with your game folder and a NosCore account, then open http://127.0.0.1:8077/
python recomp\web\serve.py --game "C:\Program Files (x86)\Nostale" --user <account> --password <password>

serve.py mints the launcher's auth code from the NosCore WebApi for that account, or you can pass one with ?auth=<code>.

Linux

The same pipeline runs on Linux (Python 3 with capstone and pefile, Emscripten's emcc on PATH, Ghidra 12 with its JDK, Node with Playwright). Generated code and builds go to $NOSRECOMP_WORK (default ~/re/work).

GHIDRA_HOME=/opt/ghidra tools/decompile.sh ~/Nostale/NosCore.exe        # Ghidra only: IDR needs Windows
W=${NOSRECOMP_WORK:-~/re/work}
python3 recomp/lift.py $W/input/NosCore.exe $W/functions.txt $W/recomp/gen --seeds $W/recomp/seeds.txt
python3 recomp/wasm/compile_all.py --web
python3 recomp/web/serve.py --game ~/Nostale --user <account> --password <password>
python3 recomp/web/iterate.py      # seeds each function the client stops on, re-lifts and rebuilds

Without IDR's seeds the function list is shorter; the lifter takes unit initialization and finalization routines from the client's init table, and iterate.py is the browser counterpart of iterate.ps1 for whatever is still only reached indirectly.

Scripted runs

node recomp/web/drive.mjs [--maps 2,20,145] [--trace] [--dump-frame] (Playwright with the installed Chrome) logs in, enters the world, walks, chats, opens the game windows and teleports between maps, then saves screenshots and the client log to C:\tools\re\work\drive\. It is the starting point for NosCore end-to-end tests.

Layout

Path	What
recomp/lift.py	x86 → C lifter
recomp/runtime/	runtime shared by the native and browser builds
recomp/port/	portable Windows host (HLE of the client's DLLs) and the WebGL renderer
recomp/web/	page, worker, dev server with socket relay, drive.mjs
recomp/wasm/	Emscripten build scripts
recomp/difftest/	differential testers: lifted instructions against Unicorn, hand-written functions against their lifted bodies
tools/	decompilation pipeline (IDR, Ghidra scripts, cross-reference queries)
symbols/<md5>/	names, packet handler tables and recompilation seeds for one client build
docs/STATUS.md	current state, lessons learned, how to continue

Disclaimer

NosTale is a trademark of Gameforge. This project is not affiliated with or endorsed by Gameforge. It contains no client code or assets; it is tooling for interoperability testing of NosCore with a client you already have.

License

MIT