How to check the nRF is connected with MQTT broker or not?

[Waqar Ahmed]

Hi,
I am facing an issue, I am developing nRF9160 based Product, get sensor data  from peripherals and publish to AWS cloud.my firmware is based on AWS IoT sample. I observed that some time devices get disconnected from AWS.I missed the sensor data during that period.
1.Now I want to save data into SD card  during  that disconnected period.? So I need find Exact point in my application which shows that it is disconnected so I log data into SD card.
2.Once if I done it successfully, log the data then I want to send this file to AWS over MQTT when it again connected?

if I place check on shadow_update ( .So for test purpose I remove the antenna from Device while application is running .its Still updating the Shadow(although message not reached on AWS ).how to kill this issue?

static void shadow_update_work_fn(struct k_work *work)
{
int err;

err = shadow_update(false);
if (err) {
printk("shadow_update, error: %d\n", err);
}

printk("Next data publication in %d seconds\n", publication_interval_seconds);

k_delayed_work_submit(&shadow_update_work, K_SECONDS( publication_interval_seconds));
}

Thanks 

[Waqar Ahmed]

I am using SDK 1.5.0

[Didrik Rokhaug]

Hi,

In some cases, it might not be possible to detect that the connection with the server has been broken until you try to send something (either keepalive messages or data).

A good place to start is in AWS IoT event handler. If you get a AWS_IOT_EVT_DISCONNECTED event, you are no longer connected.

In addition to the AWS IoT events, you can also keep track of the LTE link. Both +CEREG notifications, but also +CGEV notifications.

Best regards,

Didrik

[Waqar Ahmed]

Hi Thanks for reply.
even I tested this thing .Even by worst case remove the antenna  during the application running. Still it Publishing the message Message are not reaching on broker).but no AWS_IOT_EVT DISCONNECTED happen? 

[Didrik Rokhaug]

How long after disconnecting the antenna did you wait?

How often do you send data or keepalive messages?

Do you use PSM?

Have you tried to keep track of the AT command notifications from my last reply to see if the LTE link is dropped?

[Waqar Ahmed]

Hi Thank you for you response.
they continuously updating at some point device get reboot.
I am publishing message every 5 min.
yes, I am using PSM.
I am still monitoring the device but I am not getting any notification. I enable notification from this command

AT+CGEREP=1
 not getting these notification 

+CGEV: NW DETACH

Mobile Equipment (ME) detach:

+CGEV: ME DETACH

Thanks
 

[Didrik Rokhaug]

When you are in PSM, it makes sense that you don't get any notifications that you are disconnected, at least until you try to send something.

Could you take a modem trace, so I can see what the modem does?

[Waqar Ahmed]

Hi Didrik,
thanks for reply, now I add the CGEV notification in my application and look for CEREG status before publishing the message.
so after calling update function, I am sending CEREG command.so then from that response I can check network status.


now I am getting  in 2nd Part of query.

I successfully retrieve  data from SD card. the that is about 6KB.i had split this data to about 512 chunks.
Now I want to send these chunks in shadow update function, by using  err += json_add_str(reported_obj,"SD_DATA",sd_data1);
sd_data1 contain the chunk.

but it will give me error in this function

message = cJSON_Print(root_obj);
if (message == NULL) {
printk("cJSON_Print, error: returned NULL\n");
err = -ENOMEM;
goto cleanup;
}