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

[Hakon]

That seems to be unintended behaviour, so I reported it internally.

[Hakon]

What network and SIM are you using when you run into this error?

[Nikil Rao]

A 1nce sim card which uses Telekom band 8

[Nikil Rao]

We received sim cards from Telekom and I managed to get them to work. I also found out that this problem disappeared when I switched to the Telekom sim card! Do you know why that could be the case?

[Hakon]

It could be a roaming issue. With the 1nce SIM card it could be that you were experiencing a NAT timeout. With the Telekom SIM you're obviously not roaming, so the NAT timeout should be less likely to occur. Still hard to tell without a modem trace.