WZL-MQTT

Current stable version: 2.6.1

Documentation

For the full API documentation, view https://iot.wzl-mq.rwth-aachen.de/documentation/libs/mqtt/.

Installation

Requires at least Python 3.6

1. Install the WZL-MQTT package via pip

pip install wzl-mqtt

Usage

Publish messages

from wzl import mqtt

# username and password required to connect to the broker
MQTT_USER = ""
MQTT_PASSWORD = ""

# address, port and virtual host of the broker to connect to 
MQTT_BROKER = "127.0.0.1"
MQTT_PORT = 1883
MQTT_VHOST = "/"

# initialize publisher and connect to the broker
client = mqtt.MQTTPublisher()
client.connect(MQTT_BROKER, MQTT_USER, MQTT_PASSWORD, vhost=MQTT_VHOST, port=MQTT_PORT)

# create message and publish the message as UTF-8 encoded string
message = json.dumps({"value": [random.uniform(0, 5) for i in range(3)], "timestamp": datetime.datetime.utcnow().isoformat() + "Z",
                                  "covariance": [[2, 0, 0], [0, 2, 0], [0, 0, 0]], "nonce": str(uuid.uuid4()), "hash": None, "unit": "MTR"})
client.publish(MQTT_USER + "/channel-001", message.encode("utf-8"))

Subscribe to topics and receive messages

from wzl import mqtt

# username and password required to connect to the broker
MQTT_USER = ""
MQTT_PASSWORD = ""

# address, port and virtual host of the broker to connect to 
MQTT_BROKER = "127.0.0.1"
MQTT_PORT = 1883
MQTT_VHOST = "/"

# initialize logger
logger = mqtt.Logger.get('Receiver') # change 'Receiver' to any string you like

# define callback which will be executed when a message is received
def print_mqtt_message(topic, message):
        logger.info("### {} ###\r\n{}\r\n".format(topic, message.decode("utf-8")))

# initialize subscriber and connect to the broker   
client = mqtt.MQTTSubscriber()
client.connect(MQTT_BROKER, MQTT_USER, MQTT_PASSWORD, vhost=MQTT_VHOST, port=MQTT_PORT)

# register the callback and subscribe topic
client.set_callback("PRINT", print_mqtt_message)
client.subscribe('#')

# start waiting loop to prevent program from exiting
while True:
    try:
        time.sleep(1)
    except KeyboardInterrupt:
        break

Changelog

2.6.1 - 2024-01-11

• decoupled name of the client used locally from the name used when connecting to the broker to ensure independent clients using this library can use the same names locally

2.6.0 - 2024-01-10

• added the classmethod "client_names()" to client to retrieve the name of all instances
• the classmethod "get(username)" of the client raises the "ChildNotFoundError" if there is no instance having the specified username

2.5.4 - 2023-04-18

• fixed usage of a randomized client_id, so that the same credentials can be used for multiple clients in parallel

2.5.3 - 2023-04-15

• if the port is specified as string it is also correctly processed now
• improved user feedback in case of successful connection to the broker
• improved user feedback if the combination of port, ssl and websocket is invalid

2.5.2 - 2023-03-29

• client handles slash in at the end of prefix and the beginning of topic to avoid multiple consecutive slashes correctly now

2.5.1

• increased verbosity in case of errors by including the full stack trace

2.5.0

• changed signature of connect method
  • specifying the port is optional now, if not specified the port automatically is derived from the "websocket" and "ssl" flags

2.4.2

• fixed a bug of websocket connection

2.4.1

• made the error message of code 1 more precise

2.4.0

• added vhost parameter to connect function of client
• changed default logging behaviour
  • now by default logging is only written to console
  • if logging should also create log-files, the logger must be explicitly initialized

2.3.0

• a prefix can now be defined which is prepended to every published or subscribed topic

2.2.0

• it is possible to connect with more than one client with an identical username to the broker

2.1.0

• removed wzl-utilities dependency

2.0.0

• renamed the MQTReceiver to MQTTSubscriber for the sake of convenience
• added extensive documentation

1.3.0

• added wzl-utilities dependency by sourcing out logging functionality