wildfirechat/im-server

Wildfire IM Server is a complete instant messaging and real-time audio/video platform that companies can run entirely on their own servers. Think of it as the behind-the-scenes engine that powers chat apps like WeChat or Slack, but one you own and control rather than renting from a third party. It is written in Java and maintained by a Beijing-based company called Wildfire Infinite Network Technology. The server is designed to be light on resources, capable of running on just 128MB of RAM, while still handling large deployments with millions of users online at the same time. It uses a communication protocol called MQTT combined with Protobuf, a compact data format, to keep messages fast and bandwidth usage low. The community version and mobile client code are free for commercial use, and the company offers a professional edition for businesses that need higher scale. Client apps are available across nearly every platform: Android, iOS, web browsers, WeChat mini-programs, Windows, Mac, and Linux. Up to four devices can be logged in at once, with messages and read status kept in sync across all of them. Audio and video calling is included, with support for group video calls, 1080P quality, conference mode for large meetings, and server-side recording. Because everything runs on your own infrastructure, no data passes through a third-party cloud. The network connections are encrypted, and the on-device database is also encrypted. The server ships as a single package with few external dependencies, and the quick-start guide describes deploying both the IM server and a companion app server with a handful of commands. The repository is the core IM server only. Separate open-source repositories in the same organization cover Android and iOS client SDKs, a PC client, a web client, a push notification server, a chatbot server, a file storage service, and an open application platform for building custom integrations. Documentation is available online in Chinese.