Examples: IOT protocols with transparent mode Get started with MQTT
Digi XBee® 3 Cellular LTE Cat 1 AT&T Smart Modem User Guide
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mqttc.loop_start() # Start networking daemon
mqttc.publish("digitest/test1", "Hello, World!") # Publish message to
“digitest /test1” topic
mqttc.loop_stop() # Kill networking daemon
Note You can easily copy and paste code from the online version of this guide. Use caution with the
PDF version, as it may not maintain essential indentations.
This example imports the MQTT library, allowing you to use the MQTT protocol via APIs in the library,
such as the connect(), subscribe(), and publish() methods.
The second line creates an instance of the client, named mqttc. The client ID is the argument you
passed in: digitest (this is optional).
In line 3, the client connects to a public broker, in this case m2m.eclipse.org, on port 1883 (the default
MQTT port, or 8883 for MQTT over TLS). There are many publicly available brokers available, you can
find a list of them here: https://github.com/mqtt/mqtt.github.io/wiki/brokers.
Line 4 starts the networking daemon with client.loop_start() to handle the background
network/data tasks.
Finally, the client publishes its message Hello, World! to the broker under the topic
digitest/backlog/test1. Any nodes (devices, phones, computers, even microcontrollers) subscribed to
that same topic on the same broker receive the message.
Once no more messages need to be published, the last line stops the network daemon with
client.loop_stop().
Example: receive messages (subscribe) with MQTT
This example describes how a client would receive messages from within a specific topic on the
broker:
import paho.mqtt.client as mqtt
def on_connect(client, userdata, flags, rc): # The callback for when the
client connects to the broker
print("Connected with result code {0}".format(str(rc))) # Print result
of connection attempt
client.subscribe("digitest/test1") # Subscribe to the topic
“digitest/test1”, receive any messages published on it
def on_message(client, userdata, msg): # The callback for when a PUBLISH
message is received from the server.
print("Message received-> " + msg.topic + " " + str(msg.payload)) #
Print a received msg
client = mqtt.Client("digi_mqtt_test") # Create instance of client with
client ID “digi_mqtt_test”
client.on_connect = on_connect # Define callback function for successful
connection
client.on_message = on_message # Define callback function for receipt of a
message
# client.connect("m2m.eclipse.org", 1883, 60) # Connect to (broker, port,
keepalive-time)
client.connect('127.0.0.1', 17300)
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