Hello, I'm writing a middleware which basically adds an SSL layer to the connection between a client and a server. The connection is bidirectional, so I need to read from each side and write to the other. The client can also close the connection at any time, in which case async_shutdown() must be called on the server's stream. The problem is, often the shutdown happens when the program is waiting on the server through async_read_some(), and the shutdown will never finish. The following code illustrates this issue: #include <iostream> #include <boost/asio.hpp> #include <boost/asio/ssl.hpp> int main(int argc, char* argv[]) { try { boost::asio::io_context io_context; boost::asio::streambuf buffer; boost::asio::ssl::context ctx(boost::asio::ssl::context::tlsv12); ctx.set_verify_mode(boost::asio::ssl::verify_none); boost::asio::ssl::stream<boost::asio::ip::tcp::socket> sock(io_context, ctx); sock.next_layer().connect(boost::asio::ip::tcp::endpoint( boost::asio::ip::make_address("127.0.0.1"), 4433)); sock.handshake(boost::asio::ssl::stream_base::client); /* "async_shutdown" won't appear unless async_read_some() * is commented out */ sock.async_read_some(buffer.prepare(1024), [](boost::system::error_code, size_t) {std::cout << "async_read_some" << std::endl;}); sock.async_shutdown([](boost::system::error_code) {std::cout << "async_shutdown" << std::endl;}); io_context.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } To reproduce, start up an SSL server: openssl genrsa -out key.pem 2048 openssl req -new -sha256 -key key.pem -out csr.csr openssl req -x509 -sha256 -days 365 -key key.pem -in csr.csr -out server.pem openssl s_server -key key.pem -cert server.pem and run the program. Notice that "async_shutdown" does not finish even if the server is killed. In practice, this leaks the memory of the shutdown handler and whatever is bound to it. The only solution I can think of would be to cancel the read operation, but there's no portable way in asio to do this. Can someone point out how to solve this? Cheers, Alexander