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  • Case ID: 336135
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NRF Cloud coap payload size limitation too small

AdrianT

Hi,

I am using NRF Cloud + coap comms to send data. However I have encountered payload size limitations that are not configurable via KConfig: sdk-nrf/subsys/net/lib/nrf_cloud/src/nrf_cloud_codec.c at main · nrfconnect/sdk-nrf

I have manually modified it to accomodate my payloads. I am also considering manually encoding my payload in cbor to avoid modifying SDK code. Is there a reason why this is limited to 64 bytes? There is no documentation pointing to the payload size limits for nrf cloud.

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    The function nrf_cloud_coap_bytes_send() is not limited to 256 (that constant is not even used in the function).

    As indicated in the modem firmware release notes (inside the zip file you download from nordicsemi.com), DTLS packets are limited in size to 1024 bytes each. So a single message cannot be larger than 1024.

    The CoAP block transfer standard allows for sending much larger messages as a series of smaller ones. The nrf_cloud_coap_bytes_send() function should already do this if the buf_len parameter is > 1024. You are still limited to the size of a buffer you can allocate in RAM. 

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    The function nrf_cloud_coap_bytes_send() is not limited to 256 (that constant is not even used in the function).

    As indicated in the modem firmware release notes (inside the zip file you download from nordicsemi.com), DTLS packets are limited in size to 1024 bytes each. So a single message cannot be larger than 1024.

    The CoAP block transfer standard allows for sending much larger messages as a series of smaller ones. The nrf_cloud_coap_bytes_send() function should already do this if the buf_len parameter is > 1024. You are still limited to the size of a buffer you can allocate in RAM. 

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