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

Event Notification 235
Subscription API
Expires Header
Defines the lifetime of the subscription. Before sending an initial SUBSCRIBE
request, you may set the Expires header value for the subscription. The expires
value must be smaller than RVSIP_SUBS_EXPIRES_VAL_LIMIT value
(4000000). This value will be set in the SUBSCRIBE request as the requested
expiration time. The notifier, however, may shorten the expiration value by
setting an Expires header with a lower value in the 2xx response. The subscriber
can update the expiration value of the subscription later, by sending a refresh
request. In this case too, the notifier can shorten the requested expiration value
in the 200 response. The notifier can also shorten the subscription expiration
value by sending a NOTIFY request with the Expires parameter in the
Subscription-state header. You can get the last expiration value that was set for
the subscription at all stages of the subscription. You can only set the expiration
value before sending the initial SUBSCRIBE request. Note that for all cases
(initial SUBSCRIBE, refresh, and an expires parameter in a NOTIFY request)
the expires value must be smaller than RVSIP_SUBS_EXPIRES_VAL_LIMIT
value (4000000).
Requested Expires
The expires value that was within the SUBSCRIBE request that was received
from the subscriber.
Remaining Time
The remaining time of a subscription, in seconds.
Dialog Parameters (To, From, CallId, Cseq etc.)
A subscription created inside a call-leg takes the call-leg dialog parameters. An
independent subscription has its own dialog, therefore To and From parameters
should be set in the dialog. You can get the dialog handle from the subscription
(in a RvSipCallLegHandle format) and use it to examine other dialog
parameters.
Note The To and From parameters can only be set by using the subscription
initialization function and not the dialog handle. The dialog handle can be used for
the other dialog parameters.