Gateway Warning - could not decode client ID

ChirpStack Gateway Bridge
1

Hello, since version 3.11.0 I get following warning:

user.warn chirpstack-gateway-bridge[9842]: time=“2017-01-07T20:56:56.07667604Z” level=warning msg=“integration/mqtt/auth: could not decode client ID to gateway ID” client_id=LoRaWanAP-45-Gaerberbach error=“encoding/hex: invalid byte: U+004C ‘L’”

Any hints on what that does mean?

thx

2

It means the configured client_id can’t be decoded as Gateway ID. This is a warning, not an error. If you configure the client_id to the Gateway ID (e.g. “0102030405060708”), then this will enable the MQTT last-will and testament feature :slight_smile:

1 Like
3

Hello @brocaar

as far as I understand, the Testamanet and Last-Will function is there to let the client tell the broker what will happen when the connection to the broker is aborted.

this happens automatically if the client_id = DevEUI.

My question: what is the “default-last-will” of Chirpstack Gateway Bridge? And where can this be customized?

4

If the client_id can be decoded to a Gateway ID, it will set a retained message containing the Gateway ID + connected state. Then if it disconnects, the LWT triggers sending a retained message containing the Gateway ID + disconnected state.

5

thank you - makes it a bit more clear.
so if the gateway disconnects, LWT sends Gateway ID + disconneected state.

why is this good? what does chirpstack do with this infomation?

6

It is (currently) not used by ChirpStack itself, but it can be used by external monitoring software to monitor which gateways are connected / disconnected. E.g. if a gateway often disconnects and you don’t monitor the MQTT broker logs, you might never know that a gateway has connectivity issues. By making this connection state message retained, you can at every time query the connection state of a given Gateway ID.

3 Likes
7

i have now configured this “feature”.
now i get the messages in protobuf format.

is there any example how to “decode” this? maybe in python? i can’t find anything in the docs.

thx

8

its me again :wink:

sorry, i found it out by myself. if anyone else needs a python example - here you go.
its not a clean script, but it does check “ConnState” on mqtt.

from google.protobuf.json_format import Parse
import chirpstack_api.gw as gateway
import paho.mqtt.client as mqtt #import the client

import variables

#Variables:
mqtt_server = variables.mqtt_server
mqtt_port = variables.mqtt_port
mqtt_topic = variables.mqtt_topic
mqtt_client_id = variables.mqtt_client_id
mqtt_ca_certs = variables.mqtt_ca_certs


def unmarshal(message, pl):
    pl.ParseFromString(message)
    return pl

def on_connect(client, userdata, flags, rc):
    if rc==0:
        print("The Application has successfull connected to the MQTT broker %s on port %s as %s" % (mqtt_server, mqtt_port, mqtt_client_id))
        client.subscribe(mqtt_topic)
    else:
        print("Bad connection Returned code=",rc)
        db_disconnect()
        sys.exit("no connection possible")

def on_message(client, userdata, message):
    print("-------message-------------------")
    conn = unmarshal(message.payload, gateway.ConnState())
    print("Got: Gateway: %s with Message %s" % (conn.gateway_id.hex(), conn.state))
    print(conn)


#MQTT
client = mqtt.Client(client_id=mqtt_client_id)
client.tls_set(ca_certs=mqtt_ca_certs)
client.on_connect = on_connect
client.on_message = on_message

client.connect(mqtt_server, port=mqtt_port, keepalive=30) #connect to broker
client.loop_forever() #start the loop

hope it helps for someone