nt will need to add a certificate or certificate callback to its configuration before it can successfully authenticate. This must be called before SSL_connect().</p>

<p>SSL_verify_client_post_handshake() requires that verify flags have been previously set, and that a client sent the post-handshake authentication extension. When the client returns a certificate the verify callback will be invoked. A write operation must take place for the Certificate Request to be sent to the client, this can be done with S