Beast
HTTP and WebSocket built on Boost.Asio in C++11
...It is designed for developers who need to build interoperable clients, servers, proxies, gateways, or custom protocol components rather than using a high-level web framework. Beast follows Boost.Asio’s asynchronous model, so it fits naturally into event-driven C++ networking applications. Its algorithms are role-agnostic, meaning the same core abstractions can be used to build client-side and server-side systems. The library provides protocol vocabulary types, parsers, serializers, examples, and reusable patterns for robust network programming. It is especially useful for C++ developers who want fine-grained control over HTTP and WebSocket behavior while staying within the Boost ecosystem.