Hi,
The stack can automatically handle authentication as clients and thus can
automatically send credentials in REQUESTs. This is the purpose of
"eXosip_add_authentication_info".
If you wish to add a WWW-Authenticate header, you need to use the
"osip_www_authenticate_xxxx" APIs and add the header yourself in
the SIP answer after your called eXosip_message_build_answer and
before your call eXosip_message_send_answer.
The stack is first made for clients, so there is nothing automatic
for such authentication.
Regards
Aymeric