#Events

Events come through a pull-point subscription: the deck asks, the camera answers, so no callback server is needed.

def sub as onvif.Subscription init onvif.subscribe($cam, 120);
while (true) {
    def got as onvif.Pulled init onvif.pull($cam, $sub, 10, 100);
    $sub = $got.subscription;
    for (def e in $got.events) {
        if ($e.topic == "tns1:VideoSource/MotionAlarm" and maps.has($e.data, "State")) {
            io.printf("%s motion %s\n", $e.utcTime, $e.data["State"]);
        }
    }
    $sub = onvif.renew($cam, $sub, 120);
}

• onvif.subscribe (CreatePullPointSubscription) subscribes to every topic for the given seconds (10 to 86400). The subscription ends by itself then unless renewed.
• onvif.pull (PullMessages) waits up to timeoutSeconds (1 to 60) for events and returns as soon as there are any, as a Pulled: events (an empty list means none came) and subscription, the subscription with the currentTime and terminationTime the reply carried (a device may extend a subscription that is pulled). Keep that subscription for the next call. The first pull brings the current state of every property (operation Initialized); later ones the changes (Changed). More events than limit is an error.
• onvif.renew extends it; onvif.unsubscribe ends it. A pull on an ended subscription is a fault (ResourceUnknownFault in the WS-RF namespace on onvif_simple_server).

#Events

An Event has the topic with the ONVIF topic namespace written tns1: whatever prefix the camera used (tns1:RuleEngine/CellMotionDetector/Motion, tns1:VideoSource/MotionAlarm), the utcTime and operation, and the source, key and data simple items as maps. Topics differ by vendor: cell motion on Dahua is IsMotion under tns1:RuleEngine/CellMotionDetector/Motion, Hikvision and onvif_simple_server send State under tns1:VideoSource/MotionAlarm.

#Addressing

Calls on a subscription go to its address, placed like the service addresses (on the device's origin when the camera names another host), with WS-Addressing Action, To and MessageID header blocks. To is reference, the address exactly as the camera gave it, which is what a camera behind NAT expects to see. A camera that names the subscription by reference parameters (Axis: SubscriptionId) gets them back as header blocks marked IsReferenceParameter. The address keeps its path and query as given, even a Hikvision one with a raw % in it, on the device's scheme, host and port.

Push notifications (Subscribe with a consumer address) are out of scope.