umqtt.simple2 is a MQTT client for MicroPython. (Note that it uses some MicroPython 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 also work with other ports, but the library was not tested under other ports.
| Port | Version | Normal | SSL |
|---|---|---|---|
| esp8266 | 1.9.1 | OK | Test fails |
| esp32 | 1.9.1 | OK | OK |
There's a separate umqtt.robust2 module which builds on umqtt.simple2 adds the ability to reconnect. It is able to send unsent messages itself. And many more...
- 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 subscription
can 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.
ImportError: no module named 'umqtt.simple2'
Versions of micropython from http://micropython.org/download/ since version 1.12 include the umqtt library, which conflicts with the current library. To avoid conflicts, you need to change the order of importing libraries. You need to import the '/lib' libraries first and then the system libraries. Just add the following lines of code to the boot.py file:
import sys
sys.path.reverse()You can install using the upip:
import upip
upip.install("micropython-umqtt.simple2")or
micropython -m upip install -p modules micropython-umqtt.simple2You can also clone this repository, and install it manually:
git clone https://github.com/fizista/micropython-umqtt.simple2.gitManual installation gives you more possibilities:
- You can compile this library into MPY files using the
compile.shscript. - 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).
- Memory efficiency.
- Avoid infamous design anti-patterns like "callback hell".
- Support for both publishing and subscription via a single client object (another alternative would be to have separate client classes for publishing and subscription).
Based on the requirements above, there are following API traits:
- All data related to MQTT messages is encoded as bytes. This includes both message content AND topic names (even though MQTT spec states that topic name is UTF-8 encoded). The reason for this is simple: what is received over network socket is binary data (bytes) and it would require extra step to convert that to a string, spending memory on that. Note that this applies only to topic names (because they can be both sent and received). Other parameters specified by MQTT as UTF-8 encoded (e.g. ClientID) are accepted as strings.
- Subscribed messages are delivered via a callback. This is to avoid
using a queue for subscribed messages, as otherwise they may be
received at any time (including when client expects other type
of server response, so there're 2 choices: either deliver them
immediately via a callback or queue up until an "expected" response
arrives). Note that lack of need for a queue is delusive: the
runtime call stack forms an implicit queue in this case. And unlike
explicit queue, it's much harder to control. This design was chosen
because in a common case of processing subscribed messages it's
the most efficient. However, if in subscription callback, new
messages of QoS>0 are published, this may lead to deep, or
infinite recursion (the latter means an application will terminate
with
RuntimeException).
Taking into account API traits described above, umqtt pretty closely follows MQTT control operations, and maps them to class methods:
connect(...)- Connect to a server. Returns True if this connection uses persisten session stored on a server (this will be always False if clean_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 called before connect().wait_msg()- Wait for a server message. A subscription message will be delivered to a callback set with set_callback(), any other messages will 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, blocking
and 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 only
publish messages with QoS==0, never subscribe to them.
If you are using a subscription and/or sending QoS>0 messages, you must run one of these
commands ( 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.
QoS 0 and 1 are supported for both publish and subscribe. QoS2 isn't supported to keep code size small. Besides ClientID, only "clean session" parameter is supported for connect as of now.
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.
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.simple2 library and tests.py module. Then reset the device and watch the results in the console.
How to get tests up and running quickly:
cp example_test_main.py main.pyIn the main.py file, assign the appropriate values from your WiFi network to the WIFI_SSID and WIFI_PASSWORD variables.
./upload_to_device.shor
./upload_to_device.sh yes # A compiled version that takes up less memory on devices.Launching the tests:
screen /dev/ttyUSB0 115200 # or screen /dev/ttyACM0 115200
# Ctrl+D - to restart deviceConfiguring an encrypted connection with test.mosquitto.org:
openssl genrsa -out client.key
openssl req -out client.csr -key client.key -new
cat client.csr # Copy and paste on the page: https://test.mosquitto.org/ssl/ , click "submit"
# Save the certificate to the same directory as client.crt
# Dowlnoad mosquitto.org.crt
# Change key formats:
openssl x509 -in client.crt -out client.crt.der -outform DER
openssl rsa -in client.key -out client.key.der -outform DER
openssl x509 -in mosquitto.org.crt -out mosquitto.org.crt.der -outform DER
# Upload to device
ampy -d1 --baud 115200 --port /dev/ttyACM0 put ./client.key.der
ampy -d1 --baud 115200 --port /dev/ttyACM0 put ./client.crt.der
ampy -d1 --baud 115200 --port /dev/ttyACM0 put ./mosquitto.org.crt.derConfiguring keys for MQTT server(eg. mosquitto):
openssl req -new -x509 -days 365 -extensions v3_ca -keyout ca.key -out ca.crt -subj "/C=XX/ST=Home/L=Home/O=MyCA/OU=MyCA/CN=myca"
openssl genrsa -out server.key 2048
openssl req -new -out server.csr -key server.key -subj "/C=XX/ST=Home/L=Home/O=MQTT Broker/OU=MQTT Broker/CN=YourMQTTserver"
openssl x509 -req -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out server.crt -days 365
openssl rsa -in server.key -out server.key
openssl rsa -inform pem -in server.pem -outform der -out key.derConfiguring keys for MQTT server(eg. mosquitto):
openssl genrsa -out client.key 2048
openssl req -new -out client.csr -key client.key -subj "/C=XX/ST=Home/L=Home/O=MQTT Client/OU=MQTT Client/CN=YourDeviceHostName"
openssl x509 -req -in client.csr -CA ../ca.crt -CAkey ../ca.key -CAcreateserial -out client.crt -days 365
openssl rsa -in client.key -out client.key
openssl x509 -in client.crt -out client.crt.der -outform DER
openssl rsa -in client.key -out client.key.der -outform DER
ampy -d1 --baud 115200 --port /dev/ttyACM0 put ./client.key.der
ampy -d1 --baud 115200 --port /dev/ttyACM0 put ./client.crt.derConfiguring mosquitto:
mosquitto_passwd -c /etc/mosquitto/passwd
touch /etc/mosquitto/aclmosquitto.conf
per_listener_settings true persistence true persistence_location /var/lib/mosquitto/ persistent_client_expiration 4m log_dest file /var/log/mosquitto/mosquitto.log log_type all include_dir /etc/mosquitto/conf.d # MQTT, unencrypted, unauthenticated=anonymous listener 1883 0.0.0.0 socket_domain ipv4 allow_anonymous true set_tcp_nodelay true #keepalive_interval 0 max_keepalive 0 # MQTT, unencrypted, authenticated=password listener 1884 0.0.0.0 socket_domain ipv4 password_file /etc/mosquitto/passwd #acl_file /etc/mosquitto/acl set_tcp_nodelay true #keepalive 0 # MQTT, encrypted, unauthenticated listener 8883 0.0.0.0 socket_domain ipv4 allow_anonymous true cafile /etc/mosquitto/certs/ca.crt certfile /etc/mosquitto/certs/server.crt keyfile /etc/mosquitto/certs/server.key # MQTT, encrypted, client certificate required listener 8884 0.0.0.0 socket_domain ipv4 allow_anonymous true cafile /etc/mosquitto/certs/ca.crt capath /etc/mosquitto/certs/certs certfile /etc/mosquitto/certs/server.crt keyfile /etc/mosquitto/certs/server.key require_certificate true use_identity_as_username true # When set to true it tells mosquitto not to use the password file # MQTT, encrypted, authenticated listener 8885 0.0.0.0 socket_domain ipv4 password_file /etc/mosquitto/passwd cafile /etc/mosquitto/certs/ca.crt certfile /etc/mosquitto/certs/server.crt keyfile /etc/mosquitto/certs/server.key
chown -R mosquitto:mosquitto /etc/mosquitto/certs/- Wrong topic format during subscription - you'll get OSError: [Errno 104] ECONNRESET in subscribe() or MQTTException: 1 in the wait_msg()/check_msg()
- 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