ezyfox-server

EzyFox Server provides the plumbing. It supports TCP, UDP, and WebSocket protocols, so it works for mobile games, desktop games, and browser-based multiplayer.

It's free under Apache 2.0. You get a socket server framework, plugin system, cluster support, and client SDKs for multiple platforms. The architecture is designed for real-time gaming scenarios: low-latency messaging, room-based matchmaking, and user authentication.

The catch: this is a niche project with a small community. Documentation is limited and mostly example-driven. If you're evaluating real-time game servers, Colyseus (JavaScript) has a much larger community and better docs. Photon (proprietary) is the industry standard for commercial games. EzyFox fits if you specifically want Java and self-hosted, but you'll be figuring out edge cases on your own. The homepage URL pointing to star-history.com instead of actual project docs is not a confidence builder.