COAP_CLIENT_LIB request issue

[Christian77]

Hi.

I'm using nrf Connect SDK v3.0.1 and Zephyr v4.0.99 to implement a IoT device which connects to a Thingsboard server with CoAP. With the COAP_CLIENT Lib I want to download data in 945 chunks of 512 byte size.

I've used the coap_download example as a template for my implementation. I create the request and send it to the library with coap_client_req(). When the server responds, the callback function gets called in which I process the data (copy it to a queue in my case) and give a sem to tell the coap thread to cancel the request (coap_client_cancel_request()). This works as many times as I have configured in CONFIG_COAP_CLIENT_MAX_REQUESTS. After that the lib reports an error "No more free requests".

It looks for me that the cancel of the request didn't work. But maybe I didn't understand the usage of the COAP_CLIENT lib.
Are there any hints to use it correctly?

Thanks
BR
Christian

[Benjamin]

Well, since the path changes, you need to send a different request per chunk as you said. It indeed looks like the cancellation fails. Exactly where do you call coap_client_cancel_request() and what are your parameters? If you'd like, you could upload your source file or your callback function and I can have a look at it.


It should look something like this:

static void on_coap_response()
{
    /* 1. Copy payload to your queue */
    copy_to_queue();

    /* 2. Free the slot immediately */
    coap_client_cancel_request();

    /* 3. Wake up the thread that will launch the next chunk */
    k_sem_give(&ready_sem);
}

[Christian77]

Hello.

This is the callbackfunction:

static void on_coap_download_chunk_response(int16_t result_code, size_t offset, const uint8_t *payload, size_t len, bool last_block, void *user_data)
{
    coap_payload_t data;

    // Something was received, so restart keep alive timer.
    k_timer_start(&keep_alive_timer, K_MSEC(TX_KEEP_ALIVE_INTERVAL), K_MSEC(TX_KEEP_ALIVE_INTERVAL));

    LOG_INF("CoAP download chunk response, result_code=%d, offset=%u, len=%u, last_block=%d", result_code, offset, len, last_block);

    if (result_code == COAP_RESPONSE_CODE_CONTENT && last_block)
    {
        memcpy(data.payload, payload, MIN(len, CONFIG_COAP_CLIENT_BLOCK_SIZE));
        data.len = len;
        // Send it to the update task.
        k_msgq_put(&coap_payload_msgq, &data, K_FOREVER);
    }

    k_sem_give(&coap_download_chunk_done);
}

And this is the function for the request. It is called in a for loop with counting up chunk number in a thread:

static int client_download_software_chunk(uint8_t *new_sw_title, uint8_t *new_sw_version, uint16_t chunkSize, uint16_t chunkNumber)
{
    int ret;
    char path[100];

    /* Prepare the path for the request. */
    snprintf(path, sizeof(path), "sw/Fsau7Dg9Adfg4d?title=%s&version=%s&size=%d&chunk=%d", new_sw_title, new_sw_version, chunkSize, chunkNumber);
    LOG_INF("Download path: %s", path);

    /* Prepare the request parameters. */
    struct coap_client_request request = {.method = COAP_METHOD_GET,
                                          .fmt = COAP_CONTENT_FORMAT_TEXT_PLAIN,
                                          .confirmable = true,
                                          .path = path,
                                          .payload = NULL,
                                          .len = 0,
                                          .cb = on_coap_download_chunk_response,
                                          .options = NULL,
                                          .num_options = 0,
                                          .user_data = NULL};

    /* Make the request. It will be added to the coap_client_rcv thread and handled by that. */
    ret = coap_client_req(&client, sock, NULL, &request, NULL);
    if (ret)
    {
        LOG_ERR("Failed to send CoAP request, err %d", ret);
        return ret;
    }

    /* Wait for CoAP request to complete */
    k_sem_take(&coap_download_chunk_done, K_FOREVER);
    /* Cancel this request because in the next request the path will change (because of chunknumber) and there are only a few
     * different requests possible. */
    coap_client_cancel_request(&client, &request);
    // k_sleep(K_MSEC(200));
    return 0;
}

Tell me if you need more information.

Thank you.
Best Regards

Christian