Hi, The documentation (boost 1.67) of asio::basic_stream_socket::release() has the following remark: *This function is unsupported on Windows versions prior to Windows 8.1, and will fail with boost::asio::error::operation_not_supported on these platforms.* This is in accordance with the compiler warning I get when building my project (from asio basic_socket.hpp), and the runtime behavior: the native socket ownership is indeed retained by asio. For the IOCP backend! If I add the BOOST_ASIO_DISABLE_IOCP define to the build I still get the warning, but the release() appears to be working: the ownership is released and I can do whatever I want with the socket. My question: does the above comment apply only to the IOCP backend and I can use release() with the reactive socket service? Or it just happens to be working in my current setup but it's not guaranteed for others (or it leaks resources, etc...)? Regards, Gyorgy