Easiest way to subscribe to MQTT messages from Thingy91 on the nRF Cloud

[Joakim U]

Hi,

What's the easiest way to subscribe to the MQTT messages that the thingy91 sends to the nRF cloud?

I have tried setting it up with a node-red and a python client, but I'm never able to connect to the MQTT broker that is set up in the nRF cloud. I want to find out the easiest way to subscribe to these messages so that I can present them in a web application like node-red or similar.

The documentation that is found under APIs doesn't seem to help me, as I'm unable to connect to the broker. As I can see the data being sent to the nRF cloud, I figured it wouldn't be too difficult to just parse that data somewhere else.

Thanks

Best regards

Joakim Uddenfeldt

[Øyvind]

Hello Joakim, 
 

The documentation that is found under APIs doesn't seem to help me, as I'm unable to connect to the broker.

I assume you mean nRF Cloud API documentation, specifically the MQTT chapter?

Can you share how you are trying to connect?

Kind regards,
Øyvind

[Joakim U]

Hi Øyvind,

Here is what I have done:

I start by downloading and installing new certificates on my Thingy using these instructions:

https://devzone.nordicsemi.com/nordic/cellular-iot-guides/b/getting-started-cellular/posts/nrf-cloud-certificate-update

After that, I register my Thingy to my nRF account using the GUI on the nRF Cloud website

I then use the swagger gui to download the MQTT information, such as endpoint and topics using the following curl command

curl -X GET "">api.nrfcloud.com/.../account" -H "accept: application/json" -H "Authorization: Bearer

With the following python code, I try to subscribe to the messages that my thingy sends (which I can see in the nRF cloud GUI

# Import package
import paho.mqtt.client as mqtt
import ssl
import certifi

#Defining mqtt input
mqttEndpoint = "a2n7tk1kp18wix-ats.iot.us-east-1.amazonaws.com"
mqttTopicPrefix = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/"
#topics
gateways = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/a/gateways"
connections = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/a/connections"
alerts = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/a/alerts"
notifications ="prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/a/alerts/notifications"
messagesPrefix = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/m"

# Define Variables
MQTT_PORT = 8883
MQTT_KEEPALIVE_INTERVAL = 45
MQTT_TOPIC = "prod/7215a082-a8f3-4507-a03d-a7e2e0d55387/m/"


MQTT_HOST = "a2n7tk1kp18wix-ats.iot.us-east-1.amazonaws.com"
CA_ROOT_CERT_FILE = "root-CA.cert"
THING_CERT_FILE = "certificate.pem"
THING_PRIVATE_KEY = "privatekey.key"

# Define on connect event function
# We shall subscribe to our Topic in this function
def on_connect(mosq, obj, rc):
    mqttc.subscribe(MQTT_TOPIC, 0)

# Define on_message event function. 
# This function will be invoked every time,
# a new message arrives for the subscribed topic 
def on_message(mosq, obj, msg):
	print "Topic: " + str(msg.topic)
	print "QoS: " + str(msg.qos)
	print "Payload: " + str(msg.payload)

def on_subscribe(mosq, obj, mid, granted_qos):
    print("Subscribed to Topic: " + 
	MQTT_MSG + " with QoS: " + str(granted_qos))

# Initiate MQTT Client
mqttc = mqtt.Client()

# Assign event callbacks
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_subscribe = on_subscribe

# Configure TLS Set
mqttc.tls_set(certfile=THING_CERT_FILE, keyfile=THING_PRIVATE_KEY, cert_reqs=ssl.CERT_REQUIRED, tls_version=ssl.PROTOCOL_TLSv1_2, ciphers=None)


# Connect with MQTT Broker
mqttc.connect(MQTT_HOST, MQTT_PORT, MQTT_KEEPALIVE_INTERVAL)


# Continue monitoring the incoming messages for subscribed topic
mqttc.loop_forever()

However, i'm never able to connect successfully? I have tried the same with node-red, but i'm unable to connect using that as well.

Do you have any idea what I might be doing incorrectly? 

Best regards

Joakim Uddenfeldt

[Øyvind]

Hi Joakim,

Have you tried using Mosquitto to confirm the connection?  What is the Client ID you are using to connect?

-Øyvind

[Joakim U]

Hi Øyvind, 

I haven't tried Mosquitto yet, but will do that. My client ID is the following: prod-7215a082-a8f3-4507-a03d-a7e2e0d55387-account

Thanks

Best regards

Joakim Uddenfeldt

[Øyvind]

Hi Joakim, 

So I tried using Mosquitto to subscribe to my Thingy:91 using: 

 mosquitto_sub.exe -h a2n7tk1kp18wix-ats.iot.us-east-1.amazonaws.com -t prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/# --cert 237059_cert-2.pem.crt --cafile 237059_CA.pem -p 8883 --key 237059_PK-2.pem.key -d -i prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account

This outputs: 

Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account sending CONNECT
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received CONNACK (0)
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account sending SUBSCRIBE (Mid: 1, Topic: prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/#, QoS: 0, Options: 0x00)
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received SUBACK
Subscribed (mid: 1): 0
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (51 bytes))
{"appId":"TEMP","data":"25.8","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (52 bytes))
{"appId":"HUMID","data":"16.8","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (56 bytes))
{"appId":"AIR_PRESS","data":"98.6","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (51 bytes))
{"appId":"RSRP","data":"-115","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (51 bytes))
{"appId":"TEMP","data":"25.8","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (52 bytes))
{"appId":"HUMID","data":"16.7","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PUBLISH (d0, q0, r0, m0, 'prod/f1b2cfb2-e82e-4b13-819a-0db2bf5fad69/m/d/nrf-352656100830234/d2c', ... (56 bytes))
{"appId":"AIR_PRESS","data":"98.6","messageType":"DATA"}
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account sending PINGREQ
Client prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account received PINGRESP

Where did you get the certificates from? Did you use the following command from the MQTT API?

http POST https://api.nrfcloud.com/v1/account/certificates Authorization:"Bearer b09f76779f504da08ffea13814024ce545f68b3b"

Which will output:

http POST https://api.nrfcloud.com/v1/account/certificates Authorization:"Bearer b09f76779f504da08ffea13814024ce545f68b3b"
HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Connection: keep-alive
Content-Length: 3594
Content-Type: application/json
Date: Mon, 07 Oct 2019 13:21:19 GMT
Via: 1.1 4f48f90c7cc5834331dc3e65cd576297.cloudfront.net (CloudFront)
X-Amz-Cf-Id: b-pIQ0BhrpaY2QkFeNaGCX2wae7F5SLPUBkexpZOfs9U0puMBZJdJw==
X-Amz-Cf-Pop: OSL50-C1
X-Amzn-Trace-Id: Root=1-5d9b3bcd-fc5d62902b2ffacdfb8092b3;Sampled=0
X-Cache: Miss from cloudfront
x-amz-apigw-id: BMZIKFKmoAMFmsg=
x-amzn-RequestId: 950d3186-681c-4a18-b152-b5017f74afd9

{
    "certificate": "-----BEGIN CERTIFICATE-----\n[REMOVED]\n-----END CERTIFICATE-----\n",
    "clientId": "prod-f1b2cfb2-e82e-4b13-819a-0db2bf5fad69-account",
    "id": "[REMOVED]",
    "privateKey": "-----BEGIN RSA PRIVATE KEY-----\n[REMOVED]\n-----END RSA PRIVATE KEY-----\n",
    "publicKey": "-----BEGIN PUBLIC KEY-----\n[REMOVED]\n-----END PUBLIC KEY-----\n"
}

Or did you download from your nRF Cloud Account? See image below, which downloads a .json file to import to LTE Link Monitor - Certificate Manager

Kind regards,

Øyvind