static int new_session_cb(SSL *s, SSL_SESSION *sess)
{

    if (sess_out != NULL) {
        BIO *stmp = BIO_new_file(sess_out, "w");

        if (stmp == NULL) {
            BIO_printf(bio_err, "Error writing session file %s\n", sess_out);
        } else {
            PEM_write_bio_SSL_SESSION(stmp, sess);
            BIO_free(stmp);
        }
    }

    /*
     * Session data gets dumped on connection for TLSv1.2 and below, and on
     * arrival of the NewSessionTicket for TLSv1.3.
     */
    if (SSL_version(s) == TLS1_3_VERSION) {
        BIO_printf(bio_c_out,
                   "---\nPost-Handshake New Session Ticket arrived:\n");
        SSL_SESSION_print(bio_c_out, sess);
        BIO_printf(bio_c_out, "---\n");
    }

    /*
     * We always return a "fail" response so that the session gets freed again
     * because we haven't used the reference.
     */
    return 0;
}