Socket error: POLLHUP, Connection was closed by the AWS IoT broker

[Nikil Rao]

Hi, 

I'm trying to periodically send sensor data to the AWS server and followed the documentation here to connect and send data to the server. I use these configurations - 

CONFIG_LTE_PSM_REQ_RPTAU="11000001" (320 hours)

CONFIG_LTE_PSM_REQ_RAT="00000001" (2 seconds)

CONFIG_MQTT_KEEPALIVE=1200 (20 min)

I have programmed the device to send data (QOS 0), poll the socket for 2 seconds and then sleeps for a specified interval of time (sleep_time). I see that if I have the sleep time anywhere between 1 to 328 seconds, the device works without any problem. If I increase the sleep time to say 358 seconds, the first message is sent properly but the second message receives a Socket error: POLLHUP, Connection was closed by the AWS IoT broker message. I've played with the CONFIG_MQTT_KEEPALIVE value but I cannot increase the data send interval above 328 seconds. Do you have any ideas how I could debug this? Thanks in advance!

Nikil

[Nikil Rao]

Hi Heidi,

Thanks for the quick reply! I have tried decreasing it and increasing it but I have to send messages with an interval < 5 min in all cases to not get that error. According to the AWS documentation here (Under protocols->Connection inactivity (keep-alive interval)) it is mentioned that I can request a keep alive interval of 30-1200 seconds. I will try to take a modem trace and send it to you for analysis, thanks!

In case I cannot increase the data send interval (we would like to send data every 30 minutes) is the only solution to ping the AWS server frequently (every 5 minutes) and send data every 30 minutes? That would mean unnecessary power consumption every time we send a ping message. Is there any way I could avoid that?

Nikil