# butterfly: emulating DDR A online services

> butterfly emulates the e-AMUSEMENT service used by DDR A so the game can connect to a local server. Its Java code handles profiles, scores, options and rivals, with support code for the service's packet encryption and compression.

- Type: Case study
- Targets: Game · Protocol
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-09
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/skogaby/butterfly>
- Primary source: <https://github.com/skogaby/butterfly/blob/469b79a9858f2153ab9e51b8b2754b2d3d8ff94e/README.md>
- Catalog page: <https://awesomerea.org/resources/butterfly-ddr-a-service-case/>
- Record JSON: <https://awesomerea.org/resources/butterfly-ddr-a-service-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/butterfly-ddr-a-service-case/index.md)

## Requirements & limits

- **Prerequisites:** Java 11 or later on Windows, macOS or Linux.
- **Prerequisites:** Set the game's services URL to http://localhost and turn off url_slash.
- **Limits:** Change options in the server's SQLite database; the server has no web UI. Event progress is not tracked.
- **License:** Licensed under Apache-2.0.

## Primary sources

1. <https://github.com/skogaby/butterfly/blob/469b79a9858f2153ab9e51b8b2754b2d3d8ff94e/README.md>

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## 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.