async-destructor.cpp

#include <boost/asio.hpp>
#include <boost/asio/experimental/promise.hpp>
#include <boost/beast/core/tcp_stream.hpp>
#include <boost/beast/websocket/stream.hpp>

boost::asio::awaitable<void> echo(boost::beast::websocket::stream<boost::beast::tcp_stream>& stream) {
    for (;;) {
        boost::beast::flat_buffer buf;
        co_await stream.async_read(buf, boost::asio::use_awaitable);
        co_await stream.async_write(buf.data(), boost::asio::use_awaitable);
    }
}

boost::asio::awaitable<void> cancel(boost::asio::signal_set& signals, boost::asio::ip::tcp::socket& sock) {
    co_await signals.async_wait(boost::asio::use_awaitable);
    sock.close();
}

boost::asio::awaitable<void> serve(boost::asio::ip::tcp::socket sock, boost::asio::signal_set& signals) {
    boost::beast::websocket::stream<boost::beast::tcp_stream> stream(std::move(sock));
    co_await stream.async_accept(boost::asio::use_awaitable);
    auto ex = co_await boost::asio::this_coro::executor;
    auto promise = co_spawn(ex, echo(stream), boost::asio::experimental::use_promise);
    co_await co_spawn(ex, cancel(signals, boost::beast::get_lowest_layer(stream).socket()), boost::asio::use_awaitable);
}

boost::asio::awaitable<void> accept(boost::asio::ip::tcp::acceptor& acceptor, boost::asio::signal_set& signals) {
    for (;;)
        co_spawn(
            co_await boost::asio::this_coro::executor,
            serve(co_await acceptor.async_accept(boost::asio::use_awaitable), signals),
            boost::asio::detached);
}

int main() {
    boost::asio::io_context ctx;
    boost::asio::signal_set signals(ctx, SIGHUP);
    boost::asio::ip::tcp::acceptor acceptor(ctx, {boost::asio::ip::tcp::v4(), 54321});
    co_spawn(ctx, accept(acceptor, signals), boost::asio::detached);
    ctx.run();
}