Downlink confirmed packets

Hello,

I’m working on a device (class A) that only uses confirmed packets in uplink and downlink. To test, I use a MTCAP-868-041A that acts as a packet broker and a Mosquitto server.

I have written two clients :
- mqtt2sql that writes in a PostgreSQL database all uplink packets ;
- sql2mqtt that sends to a device some data (data come from command line or SQL database).

For example:

hilbert:[~/cvs/mqtt2sql] > ./sql2mqtt -h 192.168.10.103 -t "lora/00-04-a3-0b-00-13-f0-46/down" -v -q 2 -V 5 -m '{"data":"Y291Y291AA==","ack":true,"port":2}'
URL is 192.168.10.103:1883
Connecting
Connected
Publishing data of length 43

runs fine and device sends ‘ack’. If I don’t receive this ack, downling message is not confirmed and I have to send again this downlink message. I suppose there is somewhere a timeout as MTCAP or mosquitto have to delete message if it hasn’t been confirmed after a reasonable delay. But where ? In mosquitto ? In MTCAP (there is a timeout for class C device) ?

Best regards,

JB