I'm trying to implement a Windows named pipes server, based on boost asio. I'm creating a named pipe object, set it for async operation (overlapped), and then assign a pipe (windows::stream_handle) with the result.

I then create an overlapped (windows::overlapped_ptr) object, with an appropriate handler. Finally, I call the Windows API ::ConnectNamedPipe to wait asynchronously

The code looks like this:

class NamedPipeServer {
public:
    NamedPipeServer(boost::asio::io_context& io_context)
        : io_context_(io_context)
        , pipe_(io_context) 
    {
        start_accept();
    }

private:
    void start_accept() {
        HANDLE pipe_handle = ::CreateNamedPipe(
            "\\\\.\\pipe\\mypipe",
            PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
            PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
            PIPE_UNLIMITED_INSTANCES,
            512, 512, 0, nullptr);

        pipe_.assign(pipe_handle);

        // Copying overlapped to the closure will make sure it isn't released
        // after I exit the function, but when I exit the closure
        auto overlapped = std::make_shared<boost::asio::windows::overlapped_ptr>();
        overlapped->reset(io_context_, [this, overlapped](const boost::system::error_code& ec, std::size_t bytes_transferred) {
            handle_accept(ec);
        });
        ::ConnectNamedPipe(pipe_handle, overlapped->get());
    }

    void handle_accept(const boost::system::error_code& error) {
        // Here I should start read/write/etc.
        // the problem is: THIS FUNCTION IS NEVER CALLED
    }


    boost::asio::io_context& io_context_;
    std::string pipe_name_;
    boost::asio::windows::stream_handle pipe_;
};


int main() {
    boost::asio::io_context io_context;
    NamedPipeServer server(io_context);
    io_context.run();
    return 0;
}

My problem is that the handler is never called. Debugging the boost::asio code, I can see that within the function win_iocp_io_context::do_one, the call to ::GetQueuedCompletionStatus returns as soon as a client connect to the named pipe. However, the handler isn't being called, because the ready_ property (of win_iocp_operation structure) property remains 0.

So my question is: What will change ready_ to be true?