- Python Mqtt Paho
- Python Mqtt Tls
- Python Mqtt Example
- Python Mqtt Ssl
- Python Mqtt Subscribe Multiple Topics
There is a separate MQTTProtocol in each module implementing a different profile (subscriber, publiser, publisher/subscriber). The MQTTBaseProtocol and the various MQTTProtocol classes implement a State Pattern to avoid the “if spaghetti code” in the connection states. With the rise of artificial intelligence and big data, Python has become one of the most popular computer programming languages because of its elegant language style, rich libraries and easy to start. Also, it is starting to penetrate into various areas like IoT. There are many excellent MQTT client libraries on Python. The Paho Python Client provides a client class with support for both MQTT v3.1 and v3.1.1 on Python 2.7 or 3.x. It also provides some helper functions to make publishing one off messages to an MQTT server very straightforward. Using pip to install the Paho MQTT client Pip is a management tool for the Python.
In this quickstart, you send telemetry from a simulated device application through Azure IoT Hub to a back-end application for processing. IoT Hub is an Azure service that enables you to ingest high volumes of telemetry from your IoT devices into the cloud for storage or processing. This quickstart uses two pre-written Python applications: one to send the telemetry and one to read the telemetry from the hub. Before you run these two applications, you create an IoT hub and register a device with the hub.
Prerequisites
- An Azure account with an active subscription. Create one for free.
- Python 3.7+. For other versions of Python supported, see Azure IoT Device Features.
- A sample Python project from github. Download or clone the samples by using the Code button in the github repository.
- Port 8883 open in your firewall. The device sample in this quickstart uses MQTT protocol, which communicates over port 8883. This port may be blocked in some corporate and educational network environments. For more information and ways to work around this issue, see Connecting to IoT Hub (MQTT).
- Use the Bash environment in Azure Cloud Shell.
- If you prefer, install the Azure CLI to run CLI reference commands.
- If you're using a local installation, sign in to the Azure CLI by using the az login command. To finish the authentication process, follow the steps displayed in your terminal. For additional sign-in options, see Sign in with the Azure CLI.
- When you're prompted, install Azure CLI extensions on first use. For more information about extensions, see Use extensions with the Azure CLI.
- Run az version to find the version and dependent libraries that are installed. To upgrade to the latest version, run az upgrade.
Note
This article uses the newest version of the Azure IoT extension, called
azure-iot
. The legacy version is called azure-cli-iot-ext
.You should only have one version installed at a time. You can use the command az extension list
to validate the currently installed extensions.Use
az extension remove --name azure-cli-iot-ext
to remove the legacy version of the extension.Use
az extension add --name azure-iot
to add the new version of the extension.To see what extensions you have installed, use
az extension list
.Create an IoT hub
This section describes how to create an IoT hub using the Azure portal.
- Sign in to the Azure portal.
- From the Azure homepage, select the + Create a resource button, and then enter IoT Hub in the Search the Marketplace field.
- Select IoT Hub from the search results, and then select Create.
- On the Basics tab, complete the fields as follows:
- Subscription: Select the subscription to use for your hub.
- Resource Group: Select a resource group or create a new one. To create a new one, select Create new and fill in the name you want to use. To use an existing resource group, select that resource group. For more information, see Manage Azure Resource Manager resource groups.
- Region: Select the region in which you want your hub to be located. Select the location closest to you. Some features, such as IoT Hub device streams, are only available in specific regions. For these limited features, you must select one of the supported regions.
- IoT Hub Name: Enter a name for your hub. This name must be globally unique.
ImportantBecause the IoT hub will be publicly discoverable as a DNS endpoint, be sure to avoid entering any sensitive or personally identifiable information when you name it. - Select Next: Networking to continue creating your hub.Choose the endpoints that can connect to your IoT Hub. You can select the default setting Public endpoint (all networks), or choose Public endpoint (selected IP ranges), or Private endpoint. Accept the default setting for this example.
- Select Next: Management to continue creating your hub.You can accept the default settings here. If desired, you can modify any of the following fields:
- Pricing and scale tier: Your selected tier. You can choose from several tiers, depending on how many features you want and how many messages you send through your solution per day. The free tier is intended for testing and evaluation. It allows 500 devices to be connected to the hub and up to 8,000 messages per day. Each Azure subscription can create one IoT hub in the free tier.If you are working through a Quickstart for IoT Hub device streams, select the free tier.
- IoT Hub units: The number of messages allowed per unit per day depends on your hub's pricing tier. For example, if you want the hub to support ingress of 700,000 messages, you choose two S1 tier units.For details about the other tier options, see Choosing the right IoT Hub tier.
- Defender for IoT: Turn this on to add an extra layer of threat protection to IoT and your devices. This option is not available for hubs in the free tier. For more information about this feature, see Azure Security Center for IoT.
- Advanced Settings > Device-to-cloud partitions: This property relates the device-to-cloud messages to the number of simultaneous readers of the messages. Most hubs need only four partitions.
- Select Next: Tags to continue to the next screen.Tags are name/value pairs. You can assign the same tag to multiple resources and resource groups to categorize resources and consolidate billing. For more information, see Use tags to organize your Azure resources.
- Select Next: Review + create to review your choices. You see something similar to this screen, but with the values you selected when creating the hub.
- Select Create to create your new hub. Creating the hub takes a few minutes.
Register a device
A device must be registered with your IoT hub before it can connect. In this quickstart, you use the Azure Cloud Shell to register a simulated device.
- Run the following command in Azure Cloud Shell to create the device identity.YourIoTHubName: Replace this placeholder below with the name you chose for your IoT hub.MyPythonDevice: This is the name of the device you're registering. It's recommended to use MyPythonDevice as shown. If you choose a different name for your device, you'll also need to use that name throughout this article, and update the device name in the sample applications before you run them.
- Run the following command in Azure Cloud Shell to get the device connection string for the device you registered:YourIoTHubName: Replace this placeholder below with the name you chose for your IoT hub.Make a note of the device connection string, which looks like:
HostName={YourIoTHubName}.azure-devices.net;DeviceId=MyPythonDevice;SharedAccessKey={YourSharedAccessKey}
You'll use this value later in the quickstart. - You also need the Event Hubs-compatible endpoint, Event Hubs-compatible path, and service primary key from your IoT hub to enable the back-end application to connect to your IoT hub and retrieve the messages. The following commands retrieve these values for your IoT hub:YourIoTHubName: Replace this placeholder below with the name you choose for your IoT hub.Make a note of these three values, which you'll use later in the quickstart.
Send simulated telemetry
The simulated device application connects to a device-specific endpoint on your IoT hub and sends simulated temperature and humidity telemetry.
- Download or clone the azure-iot-samples-python repository using the Code button on the azure-iot-samples-python repository page.
- In a local terminal window, navigate to the root folder of the sample Python project. Then navigate to the iot-hubQuickstartssimulated-device folder.
- Open the SimulatedDevice.py file in a text editor of your choice.Replace the value of the
CONNECTION_STRING
variable with the device connection string you made a note of earlier. Then save your changes to SimulatedDevice.py. - In the local terminal window, run the following commands to install the required libraries for the simulated device application:
- In the local terminal window, run the following commands to run the simulated device application:The following screenshot shows the output as the simulated device application sends telemetry to your IoT hub:
Read the telemetry from your hub
The back-end application connects to the service-side Events endpoint on your IoT Hub. The application receives the device-to-cloud messages sent from your simulated device. An IoT Hub back-end application typically runs in the cloud to receive and process device-to-cloud messages.
Note
The following steps use the synchronous sample, read_device_to_cloud_messages_sync.py. You can perform the same steps with the asynchronous sample, read_device_to_cloud_messages_async.py.
- In another local terminal window, navigate to the root folder of the sample Python project. Then navigate to the iot-hubQuickstartsread-d2c-messages folder.
- Open the read_device_to_cloud_messages_sync.py file in a text editor of your choice. Update the following variables and save your changes to the file.
Variable Value EVENTHUB_COMPATIBLE_ENDPOINT
Replace the value of the variable with the Event Hubs-compatible endpoint you made a note of earlier. EVENTHUB_COMPATIBLE_PATH
Replace the value of the variable with the Event Hubs-compatible path you made a note of earlier. IOTHUB_SAS_KEY
Replace the value of the variable with the service primary key you made a note of earlier. - In the local terminal window, run the following commands to install the required libraries for the back-end application:
- In the local terminal window, run the following commands to build and run the back-end application:The following screenshot shows the output as the back-end application receives telemetry sent by the simulated device to the hub:
Clean up resources
If you will be continuing to the next recommended article, you can keep the resources you've already created and reuse them.
Otherwise, you can delete the Azure resources created in this article to avoid charges.
Important
Deleting a resource group is irreversible. The resource group and all the resources contained in it are permanently deleted. Make sure that you do not accidentally delete the wrong resource group or resources. If you created the IoT Hub inside an existing resource group that contains resources you want to keep, only delete the IoT Hub resource itself instead of deleting the resource group.
To delete a resource group by name:
- Sign in to the Azure portal and select Resource groups.
- In the Filter by name textbox, type the name of the resource group containing your IoT Hub.
- Esports logo creator free. To the right of your resource group in the result list, select .. then Delete resource group.
- You will be asked to confirm the deletion of the resource group. Type the name of your resource group again to confirm, and then select Delete. After a few moments, the resource group and all of its contained resources are deleted.
Next steps
In this quickstart, you set up an IoT hub, registered a device, sent simulated telemetry to the hub using a Python application, and read the telemetry from the hub using a simple back-end application.
To learn how to control your simulated device from a back-end application, continue to the next quickstart.
Latest version Released:
MQTT client for MicroPython.
Project description
umqtt.simple2 is a MQTT client for MicroPython. (Note that it uses someMicroPython shortcuts and doesn’t work with CPython).
Support MQTT Version 3.1.1 only.
It certainly works with micropython ports: esp8266 and esp32. It should alsowork with other ports, but the library was not tested under other ports.
MQTT client with more features
There’s a separate umqtt.robust2 module which buildson umqtt.simple2 adds the ability to reconnect.It is able to send unsent messages itself. And many more…
Differences between umqtt.simple and umqtt.simple2
- When sending messages from QoS=1, there is no problem with “suspending”the script while waiting for confirmation of message receipt by the server.
- When subscribing to a channel, there is no problem with “suspending”the script while waiting for confirmation of the subscription by the server.
- Information about receiving or failing to receive a message from QoS=1 or subscriptioncan only be received by registering a callback using the
set_callback_status()
method. - Currently, the module informs about errors in more detailed way. See the umqtt/errno.py file.
- The application should also not hang up when using
check_msg()
- The code compiled for MPY files, is about 30% larger than the original one.So this library has gained more functionality (maybe reliability),but this was done at the expense of the amount of code.
How and where to install this code?
You can install using the upip:
or
You can also clone this repository, and install it manually:
Manual installation gives you more possibilities: Madame butterfly opera dvd.
- You can compile this library into MPY files using the
compile.sh
script. - You can remove comments from the code with the command:
python setup.py minify
- You can of course copy the code as it is, if you don’t mind.
Please note that the PyPi repositories contain optimized code (no comments).
Design requirements
- Memory efficiency.
- Avoid infamous design anti-patterns like “callback hell”.
- Support for both publishing and subscription via a single clientobject (another alternative would be to have separate client classesfor publishing and subscription).
Python Mqtt Paho
API design
Based on the requirements above, there are following API traits:
- All data related to MQTT messages is encoded as bytes. This includesboth message content AND topic names (even though MQTT spec statesthat topic name is UTF-8 encoded). The reason for this is simple:what is received over network socket is binary data (bytes) andit would require extra step to convert that to a string, spendingmemory on that. Note that this applies only to topic names (becausethey can be both sent and received). Other parameters specified byMQTT as UTF-8 encoded (e.g. ClientID) are accepted as strings.
- Subscribed messages are delivered via a callback. This is to avoidusing a queue for subscribed messages, as otherwise they may bereceived at any time (including when client expects other typeof server response, so there’re 2 choices: either deliver themimmediately via a callback or queue up until an “expected” responsearrives). Note that lack of need for a queue is delusive: theruntime call stack forms an implicit queue in this case. And unlikeexplicit queue, it’s much harder to control. This design was chosenbecause in a common case of processing subscribed messages it’sthe most efficient. However, if in subscription callback, newmessages of QoS>0 are published, this may lead to deep, orinfinite recursion (the latter means an application will terminatewith
RuntimeException
).
API reference
Taking into account API traits described above, umqtt pretty closelyfollows MQTT control operations, and maps them to class methods:
- connect(..) - Connect to a server. Returns True if this connectionuses persisten session stored on a server (this will be always False ifclean_session=True argument is used (default)).
- disconnect() - Disconnect from a server, release resources.
- ping() - Ping server (response is processed automatically by wait_msg()).
- publish() - Publish a message.
- subscribe() - Subscribe to a topic.
- set_callback() - Set callback for received subscription messages. call(topic, msg, retained)
- set_callback_status() - Set callback for received subscription messages. call(pid, status)
- set_last_will() - Set MQTT “last will” message. Should be calledbefore connect().
- wait_msg() - Wait for a server message. A subscription message will bedelivered to a callback set with set_callback(), any other messageswill be processed internally.
- check_msg() - Check if there’s pending message from server. If yes,process the same way as wait_msg(), if not, return immediately.
wait_msg() and check_msg() are “main loop iteration” methods, blockingand non-blocking version. They should be called periodically in a loop,wait_msg() if you don’t have any other foreground tasks to perform(i.e. your app just reacts to subscribed MQTT messages), check_msg()if you process other foreground tasks too.
Note that you don’t need to call wait_msg()/check_msg() if you onlypublish messages with QoS0, never subscribe to them.
If you are using a subscription and/or sending QoS>0 messages, you must run one of thesecommands ( wait_msg() or check_msg() ).
For more detailed information about API please see the source code(which is quite short and easy to review) and provided examples.
Supported MQTT features
QoS 0 and 1 are supported for both publish and subscribe. QoS2 isn’tsupported to keep code size small. Besides ClientID, only “cleansession” parameter is supported for connect as of now.
Simple library testing
The current tests are not only to test the code, but also to check it in a real environment. Therefore, a good idea,before we use this library in our own project, is to test its operation with the MQTT broker.
Python Mqtt Tls
To test if the library works well with your device and MQTT broker,use the TestMQTT class from the tests.py module.
If you don’t have your own MQTT broker yet, you can use the free MQTT test broker (test.mosquitto.org).
There is also a sample file main.py`(`example_test_main.py),In this file we add only network configuration. Upload this file to your device with umqtt.simple2library and tests.py module. Then reset the device and watch the results in the console.
Different problems
- Wrong topic format during subscription - you’ll get OSError: [Errno 104] ECONNRESET in subscribe()or MQTTException: 1 in the wait_msg()/check_msg()
Additional resources
- https://mosquitto.org/ - Eclipse Mosquitto is an open source message broker that implements the MQTT protocol.
- https://test.mosquitto.org/ - MQTT test server
- http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html - MQTT 3.1.1 specyfication
- https://flespi.com/tools/mqtt-board - An open-source MQTT client tool for easy MQTT pub/sub, testing, and demonstration.
- https://github.com/wialon/gmqtt - Python MQTT client implementation(not for the micropython)
- https://www.hivemq.com/mqtt-essentials/ - Blog with explanation of MQTT specifications
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