HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

REFER 277
REFER-Subscription API
RvSipSubsReferInit() function, and sends the REFER message
by calling the RvSipSubsRefer() function. After the REFER
message is sent, subscription A moves to the SUBS_SENT
state.
3. Call-leg B receives the REFER request and creates a new
Refer-subscription B to handle this REFER. The new
subscription assumes the SUBS_RCVD state.
4. The application decides to accept the REFER and calls the
RvSipSubsReferAccept() function on Subscription B. A 202
response is sent back to Subscription A and a new Call-leg B1
is created. B1 is initialized and ready to contact the referenced
party. Subscription B assumes the SUBS_ACTIVE state.
5. Subscription A receives the 202 response and assumes the
SUBS_2XX_RCVD state.
6. The application sends an initial NOTIFY request from
Subscription B. It first creates a notification with the
RvSipSubsCreateNotify() function and then follows the
following steps to initialize and sent the request:
 Sets the Subscription-State header to “active” using
the RvSipNotifySetSubscriptionStateParams()
function.
 Sets the “SIP\2.0 100 trying” body in the NOTIFY
message using the RvSipNotifySetReferNotifyBody()
function.
 Sends the NOTIFY request from the new notification
by calling the RvSipNotifySend() function.
7. Calling the Connect() function on Call-leg B1 causes an
INVITE message to be sent to the referenced party.
8. Subscription A receives the NOTIFY request and calls the
RvSipSubsNotifyEv() callback to inform the application. The
application calls the RvSipNotifyAccept() function that causes
a 200 response to be sent for the NOTIFY request.
Subscription A then assumes the SUBS_ACTIVE state.
9. A 200 response is sent from Call-leg C.
10. Call-leg B1 receives the 200 response. It informs Subscription
B that it has reached a final status. Subscription B calls the
RvSipSubsReferNotifyReadyEv() callback to inform the
application that it is now time to send the final NOTIFY