Publishing downlink in python issue RAK 2245

LPWAN Developer Gateways / Concentrators
1

Hello!

I have been trying to the Pahos Python client to send a downlink message to a device I have built. I have successfully done this through the Chirpstack enqueue interface as well as the node-red application. However, I have found that all the examples I have found to do this in python do not work for me and actually have competing syntax:

They almost always use Port:1883 The node-red application uses 8080.

Node-red uses an API key and none of the examples show how to use this information.

They all vary with using quotation marks, topic structure ( /command/down vs /Device ID/down), if the message has to be json encoded, etc.

I have read all the mosquito documentation,2 books on the pathos client and mosquito, Chirpstack, TTN, Semtech chats, and somehow I have missed how to do this seemly easy thing to do. The documentation there but no real examples…particularly on API Key from what I found.

I can successfully subscribe to all the device events and I can see that the node-red message gets sent successfully, but I can not see the actual message it is sending which I understand is not python.

Does anyone have a small python stub on how to do this that they can point me to?

Thank you in advance

2

Welcome to RAK forum @bricemaclaren ,

I did this before on Chirpstack.

I ensure first that I can establish a downlink via mosquitto.

Something like this mosquitto_pub -h 192.168.1.12 -t "application/1/device/1dfb41d379772c52/command/down" -m '{"confirmed":true,"fPort":2,"data":"1234"}' -d

This is based on this documentation - MQTT - ChirpStack open-source LoRaWAN® Network Server documentation

Then this is the python script that I made to work on my previous test.

import os
import sys

import grpc
from chirpstack_api.as_pb.external import api

# Configuration.

# This must point to the API interface.
server = "192.168.1.20:8080"

# The DevEUI for which you want to enqueue the downlink.
dev_eui = bytes([0x1D, 0xFB, 0x41, 0xD3, 0x79, 0x77, 0x2C, 0x52])

# The API token (retrieved using the web-interface).
api_token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhcGlfa2V5X2lkIjoiYzA3ZTBjYzktM2E1OC00NTVlLWFhYjItNGYxNjdiOTgwN2VkIiwiYXVkIjoiYXMiLCJpc3MiOiJhcyIsIm5iZiI6MTYzMDg5NDk1Nywic3ViIjoiYXBpX2tleSJ9.-aKVGILqrPmKLA__RApxxXUre3mt8kY2slzCG899jBI"

if __name__ == "__main__":
  # Connect without using TLS.
  channel = grpc.insecure_channel(server)

  # Device-queue API client.
  client = api.DeviceQueueServiceStub(channel)

  # Define the API key meta-data.
  auth_token = [("authorization", "Bearer %s" % api_token)]

  # Construct request.
  req = api.EnqueueDeviceQueueItemRequest()
  req.device_queue_item.confirmed = False
  req.device_queue_item.data = bytes([0x01, 0x02, 0x03])
  req.device_queue_item.dev_eui = dev_eui.hex()
  req.device_queue_item.f_port = 10

  resp = client.Enqueue(req, metadata=auth_token)

  # Print the downlink frame-counter value.
  print(resp.f_cnt)

This one is based here - Python examples - ChirpStack open-source LoRaWAN® Network Server documentation

My chirpstack is the internal on my WisGate Developer when I did that test. But you can point it to your server location.

3

Excellent response! Thank you so much… I have not seen any of this code before using the grpc library. You addressed all my issues… really thank so much.

I will give it go and hopefully solve this problem.

Thank you once again…
-Bmaclaren