# Comet: reconstructing GOG Galaxy's game communication service

> Comet reimplements the game-facing GOG Galaxy Communication Service in Rust for use with alternative game launchers. It handles named SDK requests for library and authentication data, achievements, leaderboards, sessions, and overlay notifications. The project documents tracing Communication Service calls and identifies request types still pending.

- Type: Case study
- Targets: Protocol
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-06
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/imLinguin/comet>
- Primary source: <https://github.com/imLinguin/comet/blob/46c91529a07ab4d4ab0397429dc07d4f2f66431a/README.md>
- Catalog page: <https://awesomerea.org/resources/comet-gog-service-case/>
- Record JSON: <https://awesomerea.org/resources/comet-gog-service-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/comet-gog-service-case/index.md)

## Requirements & limits

- **Prerequisites:** Requires GOG access_token, refresh_token, and user_id, which may be imported from a supported launcher.
- **Prerequisites:** Some SDK versions require registration of the bundled dummy Windows service.
- **Limits:** GET_GLOBAL_STATS_REQUEST and two overlay notifications, GAME_JOIN_REQUEST_NOTIFICATION and GAME_INVITE_SENT_NOTIFICATION, are listed as unfinished.
- **License:** Licensed under Apache-2.0.

## Primary sources

1. <https://github.com/imLinguin/comet/blob/46c91529a07ab4d4ab0397429dc07d4f2f66431a/README.md>

## More in Protocols

- [PS3Sharp: reconstructing the PS3 TMAPI debug protocol](https://awesomerea.org/resources/ps3sharp-tmapi-case/index.md) · Case study
- [PFire: reconstructing an XFire server from its messaging protocol](https://awesomerea.org/resources/pfire-case/index.md) · Case study
- [poggadaj: rebuilding Gadu-Gadu backend services](https://awesomerea.org/resources/poggadaj-case/index.md) · Case study
- [volvo_vida_db: reconstructing Volvo D2 ECU communication from VIDA](https://awesomerea.org/resources/volvo-vida-d2-protocol-case/index.md) · Case study
- [UniSpy Server: rebuilding GameSpy services in Python](https://awesomerea.org/resources/unispy-server-case/index.md) · Case study
- [Validity90: reverse engineering a Validity/Synaptics fingerprint-reader protocol](https://awesomerea.org/resources/validity90-fingerprint-protocol-case/index.md) · Case study

## About this entry

The description was reviewed against primary sources.
Original editorial content: MIT. Linked projects, papers and assets retain their own rights and licenses.