Asio (C++ library)

Execution

• asio::io_context: the context for asynchronous I/O, which monitors asynchronous tasks and maintains a queue of completed operations ready to execute. Acts as an interface to the operating system's multiplexing mechanism.
• asio::executor: a lightweight handle or strategy determining where and how a function a function/completion handler should run.

Network I/O

• asio::steady_timer, asio::system_timer: time-management objects used to delay execution or enforce timeouts on operations
• asio::posix::stream_descriptor, asio::windows::stream_handle: OS-specific abstractions for native files/pipes/console streams
• asio::ip::icmp: the flags and types needed for Internet Control Message Protocol (ICMP).
  • asio::ip::udp::endpoint: the ICMP endpoint type
  • asio::ip::udp::resolver: the ICMP resolver type
  • asio::ip::udp::socket: the ICMP socket type
• asio::ip::tcp: the flags and types needed for Transmission Control Protocol (TCP).
  • asio::ip::tcp::acceptor: the TCP acceptor type
  • asio::ip::tcp::endpoint: the TCP endpoint type
  • asio::ip::tcp::iostream: the TCP iostream type
  • asio::ip::tcp::resolver: the TCP resolver type
  • asio::ip::tcp::socket: the TCP socket type
• asio::ip::udp: the flags and types needed for User Datagram Protocol (UDP).
  • asio::ip::udp::endpoint: the UDP endpoint type
  • asio::ip::udp::resolver: the UDP resolver type
  • asio::ip::udp::socket: the UDP socket type

Data representation

Used to point to memory blocks without copying data, for wrapping over arrays and sequential containers, akin to std::span<T> and std::string_view.

• asio::const_buffer: a read-only view of a memory block (for writing data out to a socket)
• asio::mutable_buffer: a writable view of a memory block (for reading incoming data in from a socket)
• asio::streambuf: a dynamically-resizing stream-style buffer (extends std::streambuf).

Concurrency control

• asio::strand: a logical executor adapter for handler execution serialization; if an asio::io_context runs across a pool of multiple threads, handlers assigned to the same asio::strand are guaranteed to execute sequentially.

Completion tokens

Completion tokens are used to specify how to receive the result of an asynchronous operation, and are passed as the last argument of any function prefixed with "async". Traditionally, this is done with callbacks/lambdas.

• asio::use_future: transforms the asynchronous function to return a std::future<T>.
• asio::use_awaitable: converts the asynchronous signature into a coroutine frame, allowing the use of co_await.