Notification without observe option

[sbernard31]

The RFC7641 - Observing Resources in the Constrained Application Protocol (CoAP) § 3.2. Notifications says :

In the event that the resource changes in a way that would cause a
normal GET request at that time to return a non-2.xx response (for
example, when the resource is deleted), the server sends a
notification with an appropriate response code (such as 4.04 Not
Found) and removes the client's entry from the list of observers of
the resource. Non-2.xx responses do not include an Observe Option.

I think that currently java-coap doesn't allow this.
Because when I try to send a 4.04 Not Found as notification, it is never sent.

I guess this is because of NotificationValidator, see :

java-coap/coap-core/src/main/java/com/mbed/coap/server/NotificationValidator.java

Lines 24 to 35 in a0c8294

	class NotificationValidator implements Filter.SimpleFilter<SeparateResponse, Boolean> {
	@Override
	public CompletableFuture<Boolean> apply(SeparateResponse obs, Service<SeparateResponse, Boolean> service) {
	if (obs.options().getObserve() == null) {
	throw new IllegalArgumentException("Notification packet should have observation header set");
	}
	if (obs.getToken().isEmpty()) {
	throw new IllegalArgumentException("Notification packet should have non-empty token");
	}
	return service.apply(obs);
	}

Not directly linked but that exception was silently ignore in my code (I mean I didn't even see a log), I don't know if there is something to improve in java-coap or in my code for this last point.

[sbernard31]

I think there is more or less same issue at CoAP client side, see

java-coap/coap-core/src/main/java/com/mbed/coap/server/messaging/CoapDispatcher.java

Lines 65 to 68 in a0c8294

	} else if (packet.isSeparateResponse() && packet.headers().getObserve() != null) {
	handleObservation(packet);
	return;
	}

[sbernard31]

any news about that ? 🙂

[szysas]

Sorry, nothing yet, I did not have time to look into it.