Fleck

Fleck is a lightweight WebSocket server implementation for C# applications. It gives developers a simple way to accept WebSocket connections without requiring inheritance-heavy frameworks, containers, or extra server dependencies. The project is designed to be easy to embed inside desktop apps, services, prototypes, tools, and custom .NET servers. Fleck exposes straightforward callbacks for connection open, close, message, binary, ping, and pong events. It does not depend on HttpListener or HTTP.sys, which makes it usable in environments where those Windows components are not appropriate. It is best suited for developers who need a small, direct WebSocket server layer rather than a full web framework.