The CoAP packet for canceling an observation (notifications) includes the Uri-Host and Uri-Path options twice

[derteufelqwe]

Description
When I unsubscribe from notifications using await client.cancelObserveProactive(obs), the CoAP UDP packet, which is sent, includes the Uri-Host and Uri-Path options twice.

Steps to Reproduce

1. Run the get_observe_async example
2. Check the options of the packet, which is sent after calling await client.cancelObserveProactive(obs)

Expected Result
Every option is present once. Like this:

• Uri-Host: californium.eclipseprojects.io
• Uri-Path: obs
• Observe: 1

Actual Result
Uri-Host and Uri-Path are duplicated. Like this:

• Uri-Host: californium.eclipseprojects.io
• Uri-Path: obs
• Uri-Host: californium.eclipseprojects.io
• Uri-Path: obs
• Observe: 1

Debugging Observations
It looks like this is somehow caused by the interaction between CoapObserveClientRelation.cancellation() copying the full options of the request packet (which include the Uri-Host and Uri-Path) and CoapResponse.getAllOptions() adding the Uri-Host and Uri-Path aswell

[shamblett]

I seem to be not seeing this or I've misinterpreted the issue.

If I break on line 76 of get_observe_async where the cancelObserveProactive(obs) is called then subsequently break on line 534 of coap_client where we call _waitForResponse and inspect the request the options are correct, i.e. the 3 you list in expected results.

CoapResponse.getAllOptions() is called in response processing, not the initial message sending.

Where do you check the options of the packet?

[derteufelqwe]

Interesting, IIRC that's what I did (at least for the first part). I'll check on monday and will test it again.

[derteufelqwe]

It's not monday anymore but I did look into the issue again and could reproduce it.
Here are the more detailed steps.

In coap_network_udp.dart add the following code to the send method

    final p = coapMessage.toUdpPayload();
    final ps = p.map((e) => e.toRadixString(16).padLeft(2, '0')).join();
    print("Sending coap message (${ps})");

Then run the get_observe_async example and check the actually sent responses with a CoAP decoder like this one. The CoAP response sent when canceling an observation should have the duplicate options

I think this makes sense, because CoapClient#cancelObserveProactive calls CoapObserveClientRelation#cancellation, which copies the options from the request.
Modify the cancelObserveProactive function like this and add a breakpoint on await send(c);

    print("--- canceling");
    var c = relation.cancellation();
    await send(c);
    relation.isCancelled = true;

You should see that c contains 3 options.

Now the send(...) function will subsequently at some point call CoapMessage#toUdpPayload, which will call serializeUdpMessage, which calls CoapMessage#getAllOptions() to add the Uri-Host and Uri-Path.
But they were already present, as they were copied from the request in relation.cancellation()

[shamblett]

Thanks for the analysis, I can see this now, should be fixed, package re published at version 9.1.2.

[derteufelqwe]

Fixed in PR #207.

Thanks for the fast fix.