nRF9160 MQTT - Receiving large (over 2kB) messages causing a disconnect

[gotrentus]

Hi

MQTT large message receiving when trying to obtain certs from aws...  

Setup

Modem: 1.3.3

nRF Connect: 2.3.0

I have seen posts 254191 & 303100 that relate to this this and discuss a number of work arounds.  To replicate I have removed all custom code and running example code on the dk

Running serial_lte_modem example and implementing native_tls  

testing against aws iot core (secure) , and hivemq (unsecure)

The data limit is in the low 2300's as the payload/topic combined. This points me away from the 2kB secure buffer as mentioned in 303100

Increased buffers in the native overlay

also found and increased the below in slm_defines.h this has little effect.

// #define SLM_AT_MAX_RSP_LEN   2100

#define SLM_AT_MAX_RSP_LEN   4096

// #define SLM_MAX_MESSAGE_SIZE NRF_SOCKET_TLS_MAX_MESSAGE_SIZE

#define SLM_MAX_MESSAGE_SIZE 4096

snap shot of log

#XMQTTEVT: 7,0

#XMQTTMSG: 21,10

nrf91/slm/mqtt/topic0

aaaasdfsad

 

#XMQTTEVT: 2,0

#XMQTTMSG: 21,10

nrf91/slm/mqtt/topic0

aaaasdfsad

 

#XMQTTEVT: 2,0

#XMQTTEVT: 1,-113    

%CESQ: 68,3,17,2

%CESQ: 255,0,255,0

any help much appreciated

Trent

[Charlie]

Hi Trent,

I cannot find ticket 299981. According to your description, yes, the line ending is the cause of the issue and it is not easy to manage it for certificate writing by hand.

You need either use CERTIFICATE MANAGER in LTE Link Monitor or some script like introduced in (+) Automating nRF91 TLS credential management via serial port AT commands - Software and Protocols - Cellular IoT guides - Nordic DevZone (nordicsemi.com).

Best regards,

Charlie

[gotrentus]

Hi Charlie, 

my bad, the case was 299891 nRF9160, SLM Firmware behaves incorrectly after activating Native TLS (critical problems)   

thanks, i will check that link out.

[gotrentus]

Hi Charlie,

i got it to work, using the following commands to load certs

AT#XCMNG=0,1111,0,"<CA cert>   

AT#XCMNG=0,1111,1,"<cert>   

AT#XCMNG=0,1111,2,"<private key>   

the key is to not use LTE Link Monitor, as the issues is how the LF  /   CR LF's are handled.  

I was advised to use Teraterm, making sure to set the new line transmit value to CR+LF   That way the LF within the Cert that AWS generates is replaced correctly.   

I had previously tried adding the CR manually to each line in notepad++ but it doesn't appear to have the same effect.  

if anyone gets stuck on this, please sing out. 

again Charlie, thanks heaps for your help , it's appreciated!

cheers

Trent