BoostAsio

BoostAsio, commonly referred to as Boost.Asio, is a cross‑platform C++ library for network and low‑level I/O programming. It provides both asynchronous and synchronous operations with a single, consistent programming model, and is distributed as part of the Boost Libraries.

The core is the io_context, which manages the event loop and dispatches completion handlers. Applications initiate asynchronous operations and then return to work; the io_context runs handlers as events complete. Synchronization can be controlled with strands or the executor framework to prevent concurrent handlers from running simultaneously.

Boost.Asio offers a wide range of I/O objects, including TCP and UDP sockets, timers, serial ports, signals, and name resolution. It provides platform‑specific implementations behind a uniform API, mapping to IOCP on Windows, epoll on Linux, kqueue on macOS, and similar mechanisms on other systems. The library also includes an SSL/TLS wrapper based on OpenSSL.

The API supports both traditional callback handlers and modern coroutine‑based approaches, including stackless coroutines and, with C++20, coroutines via awaitable types. This makes it suitable for scalable network servers and clients as well as event‑driven I/O tasks.

Boost.Asio originated as a standalone library named Asio, authored by Christopher Kohlhoff, and was adopted into the Boost project. It is typically used by including boost/asio.hpp and linking against Boost.System; the library is released under the Boost Software License.