Alex's Corner - Week 4 - WiPy & Publishing/Subscribing With MQTT

[robmarkcole]

@bucknall Since I can't attend the demo live, my questions are:

1. How to handle authentification - user and password? Also can I keep passwords separate from the main code? Are passwords encrypted over the network?
2. Bandwidth - what is max rate I can push readings over MQTT?
3. Sleep mode - if I wake from sleep mode are messages that were sent whilst sleeping received?
4. The docs mention a bug on line 57, I guess you will cover addressing that https://docs.pycom.io/pycom_esp32/pycom_esp32/tutorial/includes/mqtt.html
5. One final question, is it possible to pass a variable into a running python program using MQTT? For instance, could I pass in (via MQTT) the variable which sets how frequently the Wipy takes a measurement?

Cheers!
p.s. if you do a demo, perhaps also use a local MQTT broker on your mac, with mosquitto? Seems the most generic approach to me rather than a cloud service..
p.p.s. for week 5 perhaps you could cover/mention the json library? :-)

[bucknall]

Links that I mentioned in my the live stream:

• http://www.bitreactive.com/how-fast-can-you-publish-mqtt-messages/
• http://www.hivemq.com/blog/mqtt-essentials-part-4-mqtt-publish-subscribe-unsubscribe
• https://simplifiedthinking.co.uk/2015/10/03/install-mqtt-server/

[robmarkcole]

Perfect! Is the video available to download?

[bucknall]

@robmarkcole it's hosted on YouTube so you can view it back whenever you wish. Regarding downloading it, I'm sure you can but I won't advise tools to do that as I believe it's against YouTube's Ts & Cs...!

[robmarkcole]

@bucknall MQTT up and running now, thanks!

[robmarkcole]

Hmm this working before lunch, what could be going on?

[bucknall]

@robmarkcole I have a lot of problems using hivemq, its often down - maybe try another broker? like mosquitto?

[robmarkcole]

OK great, now publishing temperature readings from my DS18B20 to my Mac via MQTT. However I note that client.connect() returns 0 even though the connection is working..

[RL-Auroraim]

Hi @bucknall

I would like to have our LoPys interpret incoming subscription messages and execute a corresponding function. How do I go about saving subscribed messages as a string variable for example so I can compare them?

[PiAir]

@RL-Auroraim You can see an example of subscribe here in the video: https://youtu.be/3NDPSbr5J14?t=12m57s that Alex posted. But it looks like he hasn't pushed that one to github yet? (correct @bucknall ?)

[bucknall]

@PiAir That's correct, I'll make sure that's updated on both the docs & GitHub! Cheers!

[RobTuDelft]

Link in Youtube description seems to link to the week 5 forum topic

[robmarkcole]

@bucknall just posted about sending images over MQTT, perhaps one for another Corner?

[audreycrist]

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[ngthanh]

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