That must be why these functions don't exist: http://openssl.org/docs/crypto/BIO_s_connect.html http://openssl.org/docs/crypto/BIO_s_connect.html While the li

That must be why these functions don't exist: http://openssl.org/docs/crypto/BIO_s_connect.html http://openssl.org/docs/crypto/BIO_s_connect.html While the library isn't what's at issue here, your assumptions are way off. IPv4-capable code doesn't magically become IPv6-capable code by virtue of running on an IPv6-capable OS. Functions like these require some tweaking to be made to use new IPv6-capable structs as well as getaddrinfo. The switch is not invisible to anyone making socket API calls.