Coap message type, confirmable/non-confirmable

RE: Coap message type, confirmable/non-confirmable

Amadeus — Thu, 01 Oct 2020 16:08:41 GMT

When I send a confirmable message, I do something like this:

otCoapSendRequest(srv_context.ot, request, &messageInfo, ack_handler, NULL);

Upon receiving a confirmable message, i.e.:

otCoapMessageGetType(message) == OT_COAP_TYPE_CONFIRMABLE

I do the following for acking:

static void send_acknowledgement(const otMessage *message, const otMessageInfo *message_info) { otMessageInfo messageInfo = get_message_info((const uint8_t*)message_info->mPeerAddr.mFields.m8); otMessage* response = otCoapNewMessage(srv_context.ot, NULL); if (response == NULL) { printk("New message error\n"); return; } otCoapMessageInitResponse(response, message, OT_COAP_TYPE_ACKNOWLEDGMENT, OT_COAP_CODE_CONTENT); otError error = otCoapMessageAppendUriPathOptions(response, COMMUNICATION_URI_PATH); if (error != OT_ERROR_NONE) { printk("URI error\n"); return; } error = otCoapSendResponse(srv_context.ot, response, &messageInfo); if (error != OT_ERROR_NONE) { printk("Send error\n"); return; } }

When I use the PUT coap code, I get a timeout error in the ack_handler() provided in otCoapSendRequest(), whereas when I use CONTENT it works as expected.

No, I have not tried to sniff the communication. I will try to do that when I have time to do so.

RE: Coap message type, confirmable/non-confirmable

Edvin — Thu, 01 Oct 2020 09:15:31 GMT

[quote user="Edvin Holmseth"]In what function call did you use OT_COAP_CODE_CONTENT instread of OT_COAP_CODE_PUT?[/quote]

I am sorry if this is really obvious, but can you please let me know where you use this?

Have you tried sniffing the connection when you use OT_CPAP_CODE_CONTENT and OT_COAP_CODE_PUT? Does it behave different? I obviously does, but if this is a bug, then a sniffer trace like this can help resolve what the issue is.

RE: Coap message type, confirmable/non-confirmable

Amadeus — Wed, 30 Sep 2020 16:50:21 GMT

Yes, I have seen that documentation and it virtually says nothing.

When I acknowledge a confirmable message, I now use OT_COAP_CODE_CONTENT instead of OT_COAP_CODE_PUT and the sender receives the acknowledgement and stops resending the confirmable message. When I used OT_COAP_CODE_PUT, the sender never received an ack and eventually timed out. Therefore, there has to be something very different going on in the openthread api depending on the coap codes, and it would be advantageous for me to know what.

I have not tried other coap types as it works with OT_COAP_CODE_CONTENT. As you can see, there is quite many - without any particular documentation on what the differences are. Indeed, one could use it as an "opcode" and dispatch the receiver to the right event handler, but there have to be more happening "under the hood" since there are api side effects depending on what coap type you choose.

RE: Coap message type, confirmable/non-confirmable

Edvin — Wed, 30 Sep 2020 08:53:13 GMT

Hello,

The enumeration that defines OT_COAP_CODE_CONTENT is part of the openthread repository (particularly this file), so I don't know any more than what this says.

In what function call did you use OT_COAP_CODE_CONTENT instread of OT_COAP_CODE_PUT?

RE: Coap message type, confirmable/non-confirmable

Amadeus — Fri, 18 Sep 2020 08:05:36 GMT

Hello, I fixed the problem by using the coap type OT_COAP_CODE_CONTENT instead of OT_COAP_CODE_PUT in the ack response.

I cannot find any documentation of what the different otCoapCode enumerations really means in terms of the coap api implementations. What difference did this change make?

RE: Coap message type, confirmable/non-confirmable

Edvin — Thu, 17 Sep 2020 14:01:46 GMT

Where is otCoapResponseHandler implemented, and what does it look like? Do you seee any Result or messageinfo? Anything that can be relevant?

Would it be possible to share a project so that I can look at what you are talking about? Is this related to the coap_client example?

RE: Coap message type, confirmable/non-confirmable

Amadeus — Thu, 17 Sep 2020 08:11:30 GMT

I zeroed the uninitialized messageInfo struct and then it worked as expected.

Now I have some questions about confirmable messaging:

- When I send a confirmable message, should I always add an otCoapResponseHandler in otCoapSendRequest()?

- At the receiving side, when receiving a confirmable message, should I always respond with a message taking an OT_COAP_TYPE_ACKNOWLEDGMENT type, by calling otCoapMessageInitResponse() (which uses the message ID and token of the received message) and otCoapSendResponse()?

When trying to do this, the otCoapResponseHandler gets called at the sender after something like 20 seconds after the confirmable request, and sometimes keeps getting called, which I reckon isn't right. What can be the reason for that?

RE: Coap message type, confirmable/non-confirmable

Edvin — Wed, 16 Sep 2020 09:22:34 GMT

Is there some way for me to reproduce this? Can you verify that the behavior is the same in NCS Version 1.3.0? If so, is it possible to zip the project folder and attach it here? I can't see anything wrong in the snippets you have sent, but I am not sure I would detect any bugs just by looking at it. Also, I am not sure of what changes you did (URI options). And I don't know what your merge looks like. Is it reproducible on nRF52840 DKs?

BR,
Edvin

RE: Coap message type, confirmable/non-confirmable

Amadeus — Mon, 14 Sep 2020 12:57:58 GMT

I understand, thank you.

I tried to change to the OpenThread CoAP API by doing this:

However, nothing is received by the server. No error messages are printed either, the program executes the whole function.

If I use the Zephyr CoAP API with the same IPv6 address as I have used in the example above, it works fine:

Is there anything obviously wrong with the function calls in the OpenThread CoAP example? Indeed, I have added the resources with the appropriate URI options, which I guess is confirmed by the fact that it works with the Zephyr implementation.

For the record, I have merged together the client and server example in the ncs so both are able to initiate traffic on the same port.

RE: Coap message type, confirmable/non-confirmable

Edvin — Fri, 11 Sep 2020 08:09:43 GMT

Hello,

Sorry for the late reply. I had to check in with our Thread team.

The coap_utils does not support confirmable communication for now. The easiest way to acheive confirmable coap communication is to use OpenThread CoAP API in a similar way to how it is presented in the coap_server sample.

There is a bug in the coap_utils.h description. In fact, coap_send_request() returns retval >= 0 on sucess, and retval < 0 on failure.

Zephyr sendto() description:

https://docs.zephyrproject.org/latest/reference/networking/sockets.html?highlight=sendto#c.zsock_sendto

Thank you for reporting the retval description bug. It has been fixed now:

https://github.com/nrfconnect/sdk-nrf/pull/2899/commits

Hopefully, this answers some of your questions.

Best regards,

Edvin