int gnutls_alert_send(gnutls_session_t session, gnutls_alert_level_t level, gnutls_alert_description_t desc);
is a gnutls_session_t structure.
is the level of the alert
is the alert description
This function will send an alert to the peer in order to inform
him of something important (eg. his Certificate could not be verified).
If the alert level is Fatal then the peer is expected to close the
connection, otherwise he may ignore the alert and continue.
The error code of the underlying record send function will be
returned, so you may also receive GNUTLS_E_INTERRUPTED or
GNUTLS_E_AGAIN as well.
On success, GNUTLS_E_SUCCESS (0) is returned, otherwise
an error code is returned.