MQTTClient API

The MQTTClient class implements the client part of MQTT protocol. It can be used to publish and/or subscribe MQTT message on a broker accessible on the network through TCP or websocket protocol, both secured or unsecured.

Usage examples

Subscriber

The example below shows how to write a simple MQTT client which subscribes a topic and prints every messages received from the broker :

import logging
import asyncio

from amqtt.client import MQTTClient, ClientException
from amqtt.mqtt.constants import QOS_1, QOS_2

logger = logging.getLogger(__name__)

async def uptime_coro():
    C = MQTTClient()
    await C.connect('mqtt://test.mosquitto.org/')
    # Subscribe to '$SYS/broker/uptime' with QOS=1
    # Subscribe to '$SYS/broker/load/#' with QOS=2
    await C.subscribe([
            ('$SYS/broker/uptime', QOS_1),
            ('$SYS/broker/load/#', QOS_2),
         ])
    try:
        for i in range(1, 100):
            message = await C.deliver_message()
            packet = message.publish_packet
            print("%d:  %s => %s" % (i, packet.variable_header.topic_name, str(packet.payload.data)))
        await C.unsubscribe(['$SYS/broker/uptime', '$SYS/broker/load/#'])
        await C.disconnect()
    except ClientException as ce:
        logger.error("Client exception: %s" % ce)

if __name__ == '__main__':
    formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
    logging.basicConfig(level=logging.DEBUG, format=formatter)
    asyncio.get_event_loop().run_until_complete(uptime_coro())

When executed, this script gets the default event loop and asks it to run the uptime_coro until it completes. uptime_coro starts by initializing a MQTTClient instance. The coroutine then call connect() to connect to the broker, here test.mosquitto.org. Once connected, the coroutine subscribes to some topics, and then wait for 100 messages. Each message received is simply written to output. Finally, the coroutine unsubscribes from topics and disconnects from the broker.

Publisher

The example below uses the MQTTClient class to implement a publisher. This test publish 3 messages asynchronously to the broker on a test topic. For the purposes of the test, each message is published with a different Quality Of Service. This example also shows to method for publishing message asynchronously.

import logging
import asyncio

from amqtt.client import MQTTClient
from amqtt.mqtt.constants import QOS_0, QOS_1, QOS_2

logger = logging.getLogger(__name__)

async def test_coro():
    C = MQTTClient()
    await C.connect('mqtt://test.mosquitto.org/')
    tasks = [
        asyncio.ensure_future(C.publish('a/b', b'TEST MESSAGE WITH QOS_0')),
        asyncio.ensure_future(C.publish('a/b', b'TEST MESSAGE WITH QOS_1', qos=QOS_1)),
        asyncio.ensure_future(C.publish('a/b', b'TEST MESSAGE WITH QOS_2', qos=QOS_2)),
    ]
    await asyncio.wait(tasks)
    logger.info("messages published")
    await C.disconnect()


async def test_coro2():
    try:
        C = MQTTClient()
        ret = await C.connect('mqtt://test.mosquitto.org:1883/')
        message = await C.publish('a/b', b'TEST MESSAGE WITH QOS_0', qos=QOS_0)
        message = await C.publish('a/b', b'TEST MESSAGE WITH QOS_1', qos=QOS_1)
        message = await C.publish('a/b', b'TEST MESSAGE WITH QOS_2', qos=QOS_2)
        #print(message)
        logger.info("messages published")
        await C.disconnect()
    except ConnectException as ce:
        logger.error("Connection failed: %s" % ce)
        asyncio.get_event_loop().stop()


if __name__ == '__main__':
    formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
    logging.basicConfig(level=logging.DEBUG, format=formatter)
    asyncio.get_event_loop().run_until_complete(test_coro())
    asyncio.get_event_loop().run_until_complete(test_coro2())

As usual, the script runs the publish code through the async loop. test_coro() and test_coro() are ran in sequence. Both do the same job. test_coro() publish 3 messages in sequence. test_coro2() publishes the same message asynchronously. The difference appears the looking at the sequence of MQTT messages sent.

test_coro() achieves:

amqtt/YDYY;NNRpYQSy3?o -out-> PublishPacket(ts=2015-11-11 21:54:48.843901, fixed=MQTTFixedHeader(length=28, flags=0x0), variable=PublishVariableHeader(topic=a/b, packet_id=None), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_0'"))
amqtt/YDYY;NNRpYQSy3?o -out-> PublishPacket(ts=2015-11-11 21:54:48.844152, fixed=MQTTFixedHeader(length=30, flags=0x2), variable=PublishVariableHeader(topic=a/b, packet_id=1), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_1'"))
amqtt/YDYY;NNRpYQSy3?o <-in-- PubackPacket(ts=2015-11-11 21:54:48.979665, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=1), payload=None)
amqtt/YDYY;NNRpYQSy3?o -out-> PublishPacket(ts=2015-11-11 21:54:48.980886, fixed=MQTTFixedHeader(length=30, flags=0x4), variable=PublishVariableHeader(topic=a/b, packet_id=2), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_2'"))
amqtt/YDYY;NNRpYQSy3?o <-in-- PubrecPacket(ts=2015-11-11 21:54:49.029691, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=2), payload=None)
amqtt/YDYY;NNRpYQSy3?o -out-> PubrelPacket(ts=2015-11-11 21:54:49.030823, fixed=MQTTFixedHeader(length=2, flags=0x2), variable=PacketIdVariableHeader(packet_id=2), payload=None)
amqtt/YDYY;NNRpYQSy3?o <-in-- PubcompPacket(ts=2015-11-11 21:54:49.092514, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=2), payload=None)fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=2), payload=None)

while test_coro2() runs:

amqtt/LYRf52W[56SOjW04 -out-> PublishPacket(ts=2015-11-11 21:54:48.466123, fixed=MQTTFixedHeader(length=28, flags=0x0), variable=PublishVariableHeader(topic=a/b, packet_id=None), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_0'"))
amqtt/LYRf52W[56SOjW04 -out-> PublishPacket(ts=2015-11-11 21:54:48.466432, fixed=MQTTFixedHeader(length=30, flags=0x2), variable=PublishVariableHeader(topic=a/b, packet_id=1), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_1'"))
amqtt/LYRf52W[56SOjW04 -out-> PublishPacket(ts=2015-11-11 21:54:48.466695, fixed=MQTTFixedHeader(length=30, flags=0x4), variable=PublishVariableHeader(topic=a/b, packet_id=2), payload=PublishPayload(data="b'TEST MESSAGE WITH QOS_2'"))
amqtt/LYRf52W[56SOjW04 <-in-- PubackPacket(ts=2015-11-11 21:54:48.613062, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=1), payload=None)
amqtt/LYRf52W[56SOjW04 <-in-- PubrecPacket(ts=2015-11-11 21:54:48.661073, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=2), payload=None)
amqtt/LYRf52W[56SOjW04 -out-> PubrelPacket(ts=2015-11-11 21:54:48.661925, fixed=MQTTFixedHeader(length=2, flags=0x2), variable=PacketIdVariableHeader(packet_id=2), payload=None)
amqtt/LYRf52W[56SOjW04 <-in-- PubcompPacket(ts=2015-11-11 21:54:48.713107, fixed=MQTTFixedHeader(length=2, flags=0x0), variable=PacketIdVariableHeader(packet_id=2), payload=None)

Both coroutines have the same results except that test_coro2() manages messages flow in parallel which may be more efficient.

Reference

MQTTClient API

MQTTClient configuration

The MQTTClient __init__ method accepts a config parameter which allow to setup some behaviour and defaults settings. This argument must be a Python dict object which may contain the following entries:

• keep_alive: keep alive (in seconds) to send when connecting to the broker (defaults to 10 seconds). MQTTClient will auto-ping the broker if not message is sent within the keep-alive interval. This avoids disconnection from the broker.

• ping_delay: auto-ping delay before keep-alive times out (defaults to 1 seconds).

• default_qos: Default QoS (0) used by publish() if qos argument is not given.

• default_retain: Default retain (False) used by publish() if qos argument is not given.,

• auto_reconnect: enable or disable auto-reconnect feature (defaults to True).

• reconnect_max_interval: maximum interval (in seconds) to wait before two connection retries (defaults to 10).

• reconnect_retries: maximum number of connect retries (defaults to 2). Negative value will cause client to reconnect infinietly.

Default QoS and default retain can also be overriden by adding a topics with may contain QoS and retain values for specific topics. See the following example:

config = {
    'keep_alive': 10,
    'ping_delay': 1,
    'default_qos': 0,
    'default_retain': False,
    'auto_reconnect': True,
    'reconnect_max_interval': 5,
    'reconnect_retries': 10,
    'topics': {
        'test': { 'qos': 1 },
        'some_topic': { 'qos': 2, 'retain': True }
    }
}

With this setting any message published will set with QOS_0 and retain flag unset except for :

• messages sent to test topic : they will be sent with QOS_1

• messages sent to some_topic topic : they will be sent with QOS_2 and retain flag set

In any case, the qos and retain argument values passed to method publish() will override these settings.