The
WebDAVNOTIFY method is called by the server whenever an event that the client has subscribed to fires. The NOTIFY method will send User Datagram Protocol (UDP) packets to the client until the subscription has timed out. The
subscription to the resource will persist after the
notification is sent by the server.
A NOTIFY method without a Subscription-ID Header is an unsolicited
notification. This can be
used if the server wants to notify all clients, for example, that the store was shut down and that
notifications
will not be working properly for some period of time. Call back responses may not occur in real time because the store may automatically coalesce events.
Because UDP packets sent by the NOTIFY method may be lost, the server will keep track of past events that have subscriptions.
The server will maintain subscriptions for which events occurred until the client sends
an acknowledgement (using the Subscription-ID Header in any method, typically the POLL Method)
that it is refreshing the subscription.
Example
The following is an example UDP Request from a server. The Uniform Resource Identifier (URI) that is used was originally specified in
the Call-Back Header of the SUBSCRIBE Method when the subscription was created.
The Subscription-ID Header is the identifier of the subscription
for the event being fired.
Request
NOTIFY httpu://www.fourthcoffee.com:8080/510 HTTP/1.1
Subscription-id: 15