SSL_set_tlsext_host_name crashes

  boost, boost-beast, c++, openssl, ssl

I’m trying to use scio_beast in a project. I understand its rather unfinished, but that should not matter much. I’ve managed to get it working pretty well.

I’m trying to connect to a server behind CloudFlare now, an I understand I need SNI for that to work.

Given the following:

using tcp           = boost::asio::ip::tcp;     //  <boost/asio/ip/tcp.hpp>
namespace websocket = boost::beast::websocket;  //  <boost/beast/websocket.hpp>
namespace ssl       = boost::asio::ssl;         //  <boost/asio/ssl.hpp>

typedef websocket::stream<ssl::stream<tcp::socket>>  SecureWebSocket;
typedef std::unique_ptr<SecureWebSocket>            SecureWebSocketPtr;

// ...

SecureWebSocketPtr m_wss;

m_sslContext = std::make_shared<ssl::context>(ssl::context::tlsv12_client);
m_wss.reset(new SecureWebSocket(m_ios, *m_sslContext.get()));

auto ssl = m_wss->next_layer().native_handle();
auto host =;
SSL_set_tlsext_host_name(m_wss->next_layer().native_handle(), host);

It does not seem to matter much where I call SSL_set_tlsext_host_name (e.g. before resolving, before async_handshake), it always crashes trying to execute 0x0000000000000000.

Source: Windows Questions C++