Re: [Contiki-developers] er-coap-13 -- code error for CoAP - NON requests?

[Kovatsch M. <kov...@in...>]

You can use the global coap_error_code as a hook just like coap-separate does.
Set it to MANUAL_RESPONSE in your resource handler and no response or empty ACK will be sent.

coap_error_code = MANUAL_RESPONSE;

The engine will also close the transaction associated to the current request.

Ciao
Matthias


Von: Gruber, Lorenz [mailto:lor...@im...]
Gesendet: Montag, 2. September 2013 17:33
An: con...@li...
Betreff: [Contiki-developers] er-coap-13 -- code error for CoAP - NON requests?

Hello,

I sending a CoAP GET request to a Erbium CoAP server. However I don't want to get an ACK nor a response back from the CoAP server. As I am using IPv6 multicast addresses to spread the CoAP GET inside the network, all the ACK/ responses increase the network traffic which is undesirable.

To my understanding of CoAP 13, when I use a NON request, no ACK is sent.
HOWEVER: the response of my GET request is still sent and I receive a 2.05 back from the server even if I set the payload inside the resource to zero.

So CoAP 13 for NON requests does not give the option to send nothing, but always automatically initiates a CoAP NON response.
The following code snippet below is from "er-coap-13-engine.c" inside the "coap_receive()" function shows what is done depending on the COAP_TYPE.

          if (message->type==COAP_TYPE_CON)
          {
            /* Reliable CON requests are answered with an ACK. */
            coap_init_message(response, COAP_TYPE_ACK, CONTENT_2_05, message->mid);
          }
          else
          {
            /* Unreliable NON requests are answered with a NON as well. */
            coap_init_message(response, COAP_TYPE_NON, CONTENT_2_05, coap_get_mid());
            // -> but what if I don't want so send back anything??
           // hack by me to solve the problem, but rather ugly
           coap_error_code=MANUAL_RESPONSE;
          }

Question:
- Is there another way to prevent that nothing is sent back for a CoAP GET? (apart from my solution indicated in the code snippet above)
- Ideally one would have the choice inside the CoAP resource handle to decide whether to send
a response or not.

Thank you very much,

Lorenz