How to use N1 to Request Modbus Data from MQTT Client?

Purpose

We publish a query hex string as an MQTT client to the topic that gateway is subscribing, then N1 reply with response RS485 hex string, then we receive this response string and decode it as registers and values.

Topology

MQTT Client----MQTT Server----UG87----(LoRa)----UC11-N1----(RS485)----Modbus slave

Topic Definition in UG87’s MQTT application

Send query from MQTT client:

Topic: /ursalink/downlink/[N1's DevEUI]

Message: 

{"confirmed":true,"fport":88,"data":"AQMAAAABhAo="}

*"confirmed": is ACK response from end-device requested? true:false

*"data": AQMAAAABhAo=(base64) = 010300000001840A(hex)

Send query from embedded network server:

Content: 010300000001840A; Port: 88

Check Point: