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marp true
author Peter Eisenlohr
theme default
class
lead
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<style> :root { --color-background: #101010; --color-foreground: #ffffff; }, codenix { background-color: black !important; color: ghostwhite; } </style>

Network Programming with ASIO and C++20 Coroutines

Peter Eisenlohr

Overview

  • Disclaimer
  • Introduction to ASIO
  • Synchronous Operations
  • Asynchronous Operations
  • Completion Tokens
  • Coroutines
  • Tasks
  • Structured Concurrency

Disclaimer

  • This presentation is NOT about the C++20 Coroutines Language Feature
  • But: To use coroutines with ASIO, you don't need to now all the gory details

What is ASIO

  • ASIO (Asynchronous Input/Output) is a cross-platform C++ library for network and low-level I/O programming. It provides a consistent asynchronous model using modern C++.

  • Key Features:

    • Header-only or standalone (no Boost required)
    • Supports synchronous and asynchronous operations
    • Works with sockets, timers, serial ports, and more
    • Integrates naturally with C++ coroutines (co_await)

  • Why Use It?

    • Efficient event-driven I/O
    • Scales well for high-performance servers and clients
    • Clean abstraction over platform-specific APIs (epoll, IOCP, etc.)
void session(tcp::socket sock)
{
   std::array<char, 1024> buffer;
   for (;;)
   {
      boost::system::error_code error;
      size_t length = sock.read_some(asio::buffer(data), error);
      if (error == asio::error::eof)
         break;
      asio::write(sock, asio::buffer(data, length));
   }
}

int main(int argc, char* argv[])
{
   asio::io_context io_context;
   tcp::acceptor acceptor(io_context, tcp::endpoint(tcp::v4(), port));
   session(acceptor.accept());
   return 0;
}
void session(tcp::socket sock)
{
   std::array<char, 1024> buffer;
   for (;;)
   {
      boost::system::error_code error;
      size_t length = sock.read_some(asio::buffer(data), error);
      if (error == asio::error::eof)
         break;
      asio::write(sock, asio::buffer(data, length));
   }
}

int main(int argc, char* argv[])
{
   asio::io_context io_context;
   tcp::acceptor acceptor(io_context, tcp::endpoint(tcp::v4(), port));
   for (;;)
      std::thread(session, acceptor.accept()).detach();
   return 0;
}

Thoughts

  • Using C++ coroutines could be simpler, but there is no library support
  • ASIO is well-established, performant and part of boost
  • Create better networking code today

Outlook

std::execution

  • P2300 std::execution
  • far away from procedural programming style
  • builds graphs of async operations at compile time
  • dedicated value, error and cancellation channels
  • gives the compiler more opportunities to optimize
  • maybe there will be some S/R based networking in the future
  • should interop with coroutines