RE: nRF9160 CoAP blockwise transfer

tkeilbach — Thu, 22 Jul 2021 20:40:53 GMT

Hi Didrik,

thank you for your reply.

We managed to get the block wise transfer to work.

The route of the confusion was that we thought the CoAP libraries does the splitting of the CoAP messaged automatically. That would have been very confienient, but in the end we did this manually by our own.

Thanks again for your help!

Thomas

RE: nRF9160 CoAP blockwise transfer

Didrik Rokhaug — Thu, 22 Jul 2021 15:00:52 GMT

Hi,

The application have to handle the blockwise transfer itself.

This means that you have to append the relevant options, and split the body yourself. You can use the coap_block_size_to_bytes() function to help calculate how many bytes to append to the message.

You also have to manage sending and/or receiving every block yourself. This is generally done by sending/receiving a request for each block.

You can find the specification for how block transfers are done here: CoAP Block Transfers.

For code samples, you can look at large_get() in zephyr/samples/net/sockets/coap_server/src/coap-server.c, send_large_coap_request in zephyr/sampls/net/sockets/coap_client/src/coap-client.c and the CoAP implementation of the download_client in nrf/subsys/net/lib/download_client/src/coap.c.

Best regards,

Didrik