NB-IoT connection lost while keeping MQTT alive

RE: NB-IoT connection lost while keeping MQTT alive

Vojislav — Wed, 17 Jul 2019 12:25:50 GMT

Hi,
Can you explain how would you handle reconnection? I am having trouble reconnecting to the server.

Best regards,
Voja.

RE: NB-IoT connection lost while keeping MQTT alive

mschweig — Mon, 01 Jul 2019 11:29:26 GMT

Hi, how do you handle the reconnection?
Where do you call the functions?

RE: NB-IoT connection lost while keeping MQTT alive

men — Tue, 11 Jun 2019 07:23:18 GMT

Hi John,

I dont't think this is the issue, because the same happens with Azure IOT hub where I have a unique client ID.

RE: NB-IoT connection lost while keeping MQTT alive

John — Sat, 08 Jun 2019 20:54:41 GMT

Can I make a suggestion, I read the iot.eclipse.org will disconnect anyone that has the same Client ID.

Try changing my-client-id to something more obscure, that's potentially unlikely to be used by someone else.

Do the same with the client that is publishing the data as well, but make it different as well.

# Appliaction
#CONFIG_MQTT_PUB_TOPIC="/my/publish/topic"
#CONFIG_MQTT_SUB_TOPIC="/my/subscribe/topic"
#CONFIG_MQTT_CLIENT_ID="my-client-id"
#CONFIG_MQTT_BROKER_HOSTNAME="iot.eclipse.org"
#CONFIG_MQTT_BROKER_PORT=1883

If I'm right you would be dumped the moment someone else comes along and connects to iot.eclipse.org with

#CONFIG_MQTT_CLIENT_ID="my-client-id"

Love t know if I'm correct.

RE: NB-IoT connection lost while keeping MQTT alive

men — Fri, 07 Jun 2019 12:11:03 GMT

Hi Håkon,

RSRP on my board is -116 dBm. On the Evalkit RSRP -82 dBm and the connection is not lost. It must be my antenna. :-(

RE: NB-IoT connection lost while keeping MQTT alive

Håkon Alseth — Thu, 06 Jun 2019 12:16:04 GMT

Hi,

I tested this, by letting it stand there and it disconnected from the broker after a while:

***** Booting Zephyr OS v1.14.99-ncs1 *****
The MQTT simple sample started
LTE Link Connecting ...
LTE Link Connected!
IPv4 Address found 0x106abb25
[mqtt_evt_handler:166] MQTT client connected!
Subscribing to: my/subscribe/topic len 18
[mqtt_evt_handler:216] SUBACK packet id: 1234
[mqtt_evt_handler:172] MQTT client disconnected -45
POLLNVAL
Disconnecting MQTT client...
Could not disconnect MQTT client. Error: -57
IPv4 Address found 0x106abb25

However, it still maintained the network connection, and successfully ran the getaddrinfo() function.

I suspect that your device lost the network connection. Could you try with at_client and check your signal strength (last parameter of AT+CESQ)?

It should return:

AT+CESQ
+CESQ: 99,99,255,255,255,46
OK

RSRP = -140 + 46 = -94 dBm signal strength at my end. Not great, but not bad either. 10 to 15 dB away from the receiver sensitivity.

Kind regards,

Håkon

RE: NB-IoT connection lost while keeping MQTT alive

men — Wed, 05 Jun 2019 08:51:43 GMT

Hi Håkon,

I've tested with "test.mosquitto.org" but it is the same result, after some time the client gets disconnected.

I suspect the problem leis with the LTE connection. This time I try to get the IP of google.com. At first it is successful and so the connection to "test.mosquitto.org", but when disconnected I'm unable to get IP of google.com:

The MQTT simple sample started
LTE Link Connecting ...
LTE Link Connected!
Testing connection to "google.com"
OK: getaddrinfo success
IPv4 Address found 0x106abb25
[mqtt_evt_handler:166] MQTT client connected!
[mqtt_evt_handler:177] MQTT client disconnected -45
POLLNVAL
Disconnecting MQTT client...
Could not disconnect MQTT client. Error: -57
Testing connection to "google.com"
ERROR: getaddrinfo failed 60

RE: NB-IoT connection lost while keeping MQTT alive

Håkon Alseth — Tue, 04 Jun 2019 13:55:22 GMT

Hi,

I agree that there's some cases here that isn't handled well in the application. When getting disconnected, the application will not try to reconnect for instance.

iot.eclipse.org isn't always the most stable broker, as there's alot of traffic going through that broker. Could you try test.mosquitto.org and see if this one also has stability issues?

Kind regards,

Håkon

RE: NB-IoT connection lost while keeping MQTT alive

men — Tue, 04 Jun 2019 11:05:01 GMT

Hi jbrzozoski,

Yes I agree, I should be handling the reconnect in a more gentle manner. But the initial problem is that the client gets disconnected from the MQTT server.

I have also tested this with Nordic MQTT sample-code and get the same result, after about 5 min the clients gets disconnected:

The MQTT simple sample started
LTE Link Connecting ...
LTE Link Connected!
IPv4 Address found 0xf11e29c6
[mqtt_evt_handler:166] MQTT client connected!
[mqtt_evt_handler:177] MQTT client disconnected -45
POLLNVAL
Disconnecting MQTT client...
Could not disconnect MQTT client. Error: -57

This is the content of prj.conf:

# General config
CONFIG_TEST_RANDOM_GENERATOR=y

# Networking
CONFIG_NETWORKING=y
CONFIG_NET_SOCKETS_OFFLOAD=y
CONFIG_NET_SOCKETS=y
CONFIG_NET_SOCKETS_POSIX_NAMES=y

# LTE link control
CONFIG_LTE_LINK_CONTROL=y
CONFIG_LTE_AUTO_INIT_AND_CONNECT=n
CONFIG_LTE_NETWORK_MODE_LTE_M=n
CONFIG_LTE_NETWORK_MODE_NBIOT=y
CONFIG_LTE_LEGACY_PCO_MODE=y

# BSD library
CONFIG_BSD_LIBRARY=y

# AT Host
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_AT_HOST_LIBRARY=y

# MQTT
CONFIG_MQTT_LIB=y
CONFIG_MQTT_LIB_TLS=n

# Appliaction
#CONFIG_MQTT_PUB_TOPIC="/my/publish/topic"
#CONFIG_MQTT_SUB_TOPIC="/my/subscribe/topic"
#CONFIG_MQTT_CLIENT_ID="my-client-id"
#CONFIG_MQTT_BROKER_HOSTNAME="iot.eclipse.org"
#CONFIG_MQTT_BROKER_PORT=1883

# Main thread
CONFIG_MAIN_THREAD_PRIORITY=7
CONFIG_MAIN_STACK_SIZE=4096

CONFIG_HEAP_MEM_POOL_SIZE=1024

RE: NB-IoT connection lost while keeping MQTT alive

jbrzozoski — Fri, 31 May 2019 15:17:10 GMT

That -114 is errno EALREADY. In my testing w/ LTE-M, the MQTT/socket libraries seemed fragile if I pounded on them too much while there was already an outstanding connection request. It was easy enough to remember if my device had an outstanding request and hold off if so. You may want to try the same thing. Just be sure to keep calling mqtt_input() while waiting for the connection to complete, since it needs to handle connection handshaking.