COAP Block Transfer with 1024 block size does not work

RE: COAP Block Transfer with 1024 block size does not work

Edvin — Mon, 02 Mar 2026 11:56:30 GMT

Not from my side, at least. There may have been some updates in NCS solving this if it was a bug, but not that I am aware of. If you are seeing the same issue, please open a new ticket, with detailed description on how to reproduce the issue you are seeing, including the NCS version and what device you are using.

Best regards,

Edvin

RE: COAP Block Transfer with 1024 block size does not work

drumpros — Mon, 02 Mar 2026 10:36:33 GMT

Hi there, Did this issue get solved? i am having a similar issue. 512 works fine but i cannot get 1024 to work on SDK 2.5.3

RE: COAP Block Transfer with 1024 block size does not work

Edvin — Fri, 09 Feb 2024 14:17:27 GMT

If you need to share something you cannot share in public, you can create a private ticket. But if it doesn't contain sensitive information, we can just continue here.

BR,
Edvin

RE: COAP Block Transfer with 1024 block size does not work

roshangeoroy — Thu, 08 Feb 2024 12:12:12 GMT

Hi Edwin,
I apologize for the late reply.

If the client and server application is absolutely necessary, can we continue this over a private ticket?

Thanks,
Rosh

RE: COAP Block Transfer with 1024 block size does not work

Edvin — Fri, 26 Jan 2024 10:21:02 GMT

Hello,

I understand. Do you have a client and server application that you can zip and upload, so that I can replicate the issue? I need to do so in order to investigate, and perhaps show it to our openthread team.

Best regards,

Edvin

RE: COAP Block Transfer with 1024 block size does not work

roshangeoroy — Wed, 24 Jan 2024 08:45:24 GMT

Hey Edwin,

Appreciate the reply. We use OpenThread CoAP API for block transfer since we are doing the communication over Thread. It has the following function 'otCoapSecureSendRequestBlockWise'

otError otCoapSecureSendRequestBlockWise(
  otInstance *aInstance,
  otMessage *aMessage,
  otCoapResponseHandler aHandler,
  void *aContext,
  otCoapBlockwiseTransmitHook aTransmitHook,
  otCoapBlockwiseReceiveHook aReceiveHook
)

With this function we send the first GET Request to the server. The consecutive requests are handled by the library. For all the other block sizes that we have tested the aReceiveHook function is called on each block's arrival.This is not happening only in the case of 1024. The function otCoapSecureSendRequestBlockWise does not return any error. But CoapResponseHandler returns a timeout error after roughly one minute.

[quote userid="26071" url="~/f/nordic-q-a/107566/coap-block-transfer-with-1024-block-size-does-not-work/465377"]What block sizes did you test? Does it work with 1025 and 1023?[/quote]

We tested using 64, 128, 256 and 512 bytes block sizes. Sizes of the blocks are provided by OpenThread as an Enum.

typedef enum otCoapBlockSzx
{
    OT_COAP_OPTION_BLOCK_SZX_16   = 0,
    OT_COAP_OPTION_BLOCK_SZX_32   = 1,
    OT_COAP_OPTION_BLOCK_SZX_64   = 2,
    OT_COAP_OPTION_BLOCK_SZX_128  = 3,
    OT_COAP_OPTION_BLOCK_SZX_256  = 4,
    OT_COAP_OPTION_BLOCK_SZX_512  = 5,
    OT_COAP_OPTION_BLOCK_SZX_1024 = 6
} otCoapBlockSzx;

The log MeshForwarder-: Received IPv6 UDP msg, len:1122, chksum:137c, ecn:no, from:0x8800, sec:yes, prio:normal, rss:-39 comes when I enable OpenThread logs using the configuration

# CONFIG_OPENTHREAD_DEBUG=y
# CONFIG_OPENTHREAD_L2_DEBUG=y
# CONFIG_OPENTHREAD_LOG_LEVEL_DEBG=y

Thanks,

Rosh

RE: COAP Block Transfer with 1024 block size does not work

Edvin — Mon, 22 Jan 2024 14:49:51 GMT

Hello,

Sorry for the late reply.

What block sizes did you test? Does it work with 1025 and 1023? Do you have an application (preferably client and server) that can reproduce the issue you are seeing? Where does the log come from?

[quote user=""]MeshForwarder-: Received IPv6 UDP msg, len:1122, chksum:137c, ecn:no, from:0x8800, sec:yes, prio:normal, rss:-39[/quote]

And does the coap_send_request() (is that the API you are using) return 0 or something else?

Best regards,

Edvin