struct socket_pair
    {
        net::io_context ioc1;
        net::ip::tcp::socket s1;

        net::io_context ioc2;
        net::ip::tcp::socket s2;

        socket_pair()
            : s1(ioc1)
            , s2(ioc2)
        {
            net::io_context ioc;
            net::ip::tcp::acceptor a(ioc);
            net::ip::tcp::endpoint ep(
                net::ip::make_address_v4("127.0.0.1"), 0);
            a.open(ep.protocol());
            a.set_option(
                net::socket_base::reuse_address(true));
            a.bind(ep);
            a.listen(
                net::socket_base::max_listen_connections);
            a.async_accept(s2,
                [](error_code ec)
                {
                    if(ec)
                        BOOST_THROW_EXCEPTION(system_error{ec});
                });
            s1.async_connect(a.local_endpoint(),
                [](error_code ec)
                {
                    if(ec)
                        BOOST_THROW_EXCEPTION(system_error{ec});
                });
            for(;;)
                if(
                    ioc.poll() +
                    ioc1.poll() +
                    ioc2.poll() == 0)
                    break;
            BOOST_ASSERT(s1.is_open());
            BOOST_ASSERT(s2.is_open());
            BOOST_ASSERT(
                s1.remote_endpoint() ==
                s2.local_endpoint());
            BOOST_ASSERT(
                s2.remote_endpoint() ==
                s1.local_endpoint());
        }
    };