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Post #24841
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Corosio Beta - coroutine-native networking for C++20
We are releasing the Corosio beta - a coroutine-native networking library for C++20 built by the C++ Alliance. It is the successor to Boost.Asio, designed from the ground up for coroutines.
**What is it?**
Corosio provides TCP sockets, acceptors, TLS streams, timers, and DNS resolution. Every operation is an awaitable. You write co\_await and the library handles executor affinity, cancellation, and frame allocation. No callbacks. No futures. No sender/receiver.
It is built on Capy, a coroutine I/O foundation that ships with Corosio. Capy provides the task types, buffer sequences, stream concepts, and execution model. The two libraries have no dependencies outside the standard library.
**An echo server in 45 lines:**
#include <boost/capy.hpp>
#include <boost/corosio.hpp>
namespace corosio = boost::corosio;
namespace capy = boost::capy;
capy::task<> echo_session(corosio::tcp_socket sock)
{
char buf[1024];
for (;;)
{
auto [ec, n] = co_await sock.read_some(
capy::mutable_buffer(buf, sizeof(buf)));
auto [wec, wn] = co_await capy::write(
sock, capy::const_buffer(buf, n));
if (ec)
break;
if (wec)
break;
}
sock.close();
}
capy::task<> accept_loop(
corosio::tcp_acceptor& acc,
corosio::io_context& ioc)
{
for (;;)
{
corosio::tcp_socket peer(ioc);
auto [ec] = co_await acc.accept(peer);
if (ec)
continue;
capy::run_async(ioc.get_executor())(echo_session(std::move(peer)));
}
}
int main()
{
corosio::io_context ioc;
corosio::tcp_acceptor acc(ioc, corosio::endpoint(8080));
capy::run_async(ioc.get_executor())(accept_loop(acc, ioc));
ioc.run();
}
**Features:**
* Coroutine-only - every I/O operation is an awaitable, no callbacks
* TCP sockets, acceptors, TLS streams, timers, DNS resolution
* Cross-platform: Windows (IOCP), Linux (epoll), macOS/FreeBSD (kqueue)
* Type-erased streams - write any\_stream& and accept any stream type. Compile once, link anywhere. No template explosion.
* Zero steady-state heap allocations after warmup
* Automatic executor affinity - your coroutine always resumes on the right thread
* Automatic stop token propagation - cancel at the top, everything below stops Buffer sequences with byte-level manipulation (slice, front, consuming\_buffers, circular buffers)
* Concurrency primitives: strand, thread\_pool, async\_mutex, async\_event, when\_all, when\_any Forward-flow allocator control for coroutine frames
* C++20: GCC 12+, Clang 17+, MSVC 14.34+
**Get it:**
git clone https://github.com/cppalliance/corosio.git
cd corosio
cmake -S . -B build -G Ninja
cmake --build build
No dependencies. Capy is fetched automatically.
Or use CMake FetchContent in your project:
include(FetchContent)
FetchContent_Declare(corosio
GIT_REPOSITORY https://github.com/cppalliance/corosio.git
GIT_TAG develop
GIT_SHALLOW TRUE)
FetchContent_MakeAvailable(corosio)
target_link_libraries(my_app Boost::corosio)
**Links:**
* Corosio: [https://github.com/cppalliance/corosio](https://github.com/cppalliance/corosio)
* Corosio docs: [https://develop.corosio.cpp.al/](https://develop.corosio.cpp.al/)
* Capy: [https://github.com/cppalliance/capy](https://github.com/cppalliance/capy)
* Capy docs: [https://develop.capy.cpp.al/](https://develop.capy.cpp.al/)
**What’s next:**
HTTP, WebSocket, and high-level server libraries are in development on the same foundation. Corosio is heading for Boost formal review. We want your feedback.
https://redd.it/1rqykml
@r_cpp
GitHub GitHub - cppalliance/corosio Contribute to cppalliance/corosio development by creating an account on GitHub. We are releasing the Corosio beta - a coroutine-native networking library for C++20 built by the C++ Alliance. It is the successor to Boost.Asio, designed from the ground up for coroutines.
**What is it?**
Corosio provides TCP sockets, acceptors, TLS streams, timers, and DNS resolution. Every operation is an awaitable. You write co\_await and the library handles executor affinity, cancellation, and frame allocation. No callbacks. No futures. No sender/receiver.
It is built on Capy, a coroutine I/O foundation that ships with Corosio. Capy provides the task types, buffer sequences, stream concepts, and execution model. The two libraries have no dependencies outside the standard library.
**An echo server in 45 lines:**
#include <boost/capy.hpp>
#include <boost/corosio.hpp>
namespace corosio = boost::corosio;
namespace capy = boost::capy;
capy::task<> echo_session(corosio::tcp_socket sock)
{
char buf[1024];
for (;;)
{
auto [ec, n] = co_await sock.read_some(
capy::mutable_buffer(buf, sizeof(buf)));
auto [wec, wn] = co_await capy::write(
sock, capy::const_buffer(buf, n));
if (ec)
break;
if (wec)
break;
}
sock.close();
}
capy::task<> accept_loop(
corosio::tcp_acceptor& acc,
corosio::io_context& ioc)
{
for (;;)
{
corosio::tcp_socket peer(ioc);
auto [ec] = co_await acc.accept(peer);
if (ec)
continue;
capy::run_async(ioc.get_executor())(echo_session(std::move(peer)));
}
}
int main()
{
corosio::io_context ioc;
corosio::tcp_acceptor acc(ioc, corosio::endpoint(8080));
capy::run_async(ioc.get_executor())(accept_loop(acc, ioc));
ioc.run();
}
**Features:**
* Coroutine-only - every I/O operation is an awaitable, no callbacks
* TCP sockets, acceptors, TLS streams, timers, DNS resolution
* Cross-platform: Windows (IOCP), Linux (epoll), macOS/FreeBSD (kqueue)
* Type-erased streams - write any\_stream& and accept any stream type. Compile once, link anywhere. No template explosion.
* Zero steady-state heap allocations after warmup
* Automatic executor affinity - your coroutine always resumes on the right thread
* Automatic stop token propagation - cancel at the top, everything below stops Buffer sequences with byte-level manipulation (slice, front, consuming\_buffers, circular buffers)
* Concurrency primitives: strand, thread\_pool, async\_mutex, async\_event, when\_all, when\_any Forward-flow allocator control for coroutine frames
* C++20: GCC 12+, Clang 17+, MSVC 14.34+
**Get it:**
git clone https://github.com/cppalliance/corosio.git
cd corosio
cmake -S . -B build -G Ninja
cmake --build build
No dependencies. Capy is fetched automatically.
Or use CMake FetchContent in your project:
include(FetchContent)
FetchContent_Declare(corosio
GIT_REPOSITORY https://github.com/cppalliance/corosio.git
GIT_TAG develop
GIT_SHALLOW TRUE)
FetchContent_MakeAvailable(corosio)
target_link_libraries(my_app Boost::corosio)
**Links:**
* Corosio: [https://github.com/cppalliance/corosio](https://github.com/cppalliance/corosio)
* Corosio docs: [https://develop.corosio.cpp.al/](https://develop.corosio.cpp.al/)
* Capy: [https://github.com/cppalliance/capy](https://github.com/cppalliance/capy)
* Capy docs: [https://develop.capy.cpp.al/](https://develop.capy.cpp.al/)
**What’s next:**
HTTP, WebSocket, and high-level server libraries are in development on the same foundation. Corosio is heading for Boost formal review. We want your feedback.
https://redd.it/1rqykml
@r_cpp
