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Paho MQTT Client (Javascript), Envoy, VerneMQ: debugging disconnects

After deploying picockpit to my server, a bug was observed: the web frontend would disconnect in very regular intervals. This had not been present on the local development environment. Users of picockpit reported the same bug. I have debugged it today, and applied a hotfix. It turns out it was a timing issue. TL;DR how [...]

By | September 8th, 2019|MQTT, PiCockpit, VerneMQ|Kommentare deaktiviert für Paho MQTT Client (Javascript), Envoy, VerneMQ: debugging disconnects

Specifying Debian dependency between two versions & apt-get installing .deb files

These informations are probably of most interest to package maintainers:Dependency on specific package versionsHere is how to specify a python3 dependency between version 3.5 (equals to or later), and 3.6 (must be earlier) in debian/control:Depends: python3 (>= 3.5), python3 (<< 3.6)So you basically specify two dependencies.Note, this will not work for Debian Buster (Raspbian buster [...]

By | August 21st, 2019|Development, Tips & tricks|Kommentare deaktiviert für Specifying Debian dependency between two versions & apt-get installing .deb files

VerneMQ how to disconnect clients forceably per command line

There is a commandvmq-admin session showwhich will show you the currently connected clients:Unfortunately, this output is truncated for a total width of 80 characters (no matter how many would fit) and there is currently no indication that it is.See this VerneMQ Github issue: https://github.com/vernemq/vernemq/issues/1200To disconnect clients you need the client_id and the mountpoint. Therefore, you [...]

By | August 8th, 2019|VerneMQ|Kommentare deaktiviert für VerneMQ how to disconnect clients forceably per command line

Paho failure to subscribe

ProblemAMQJS0005E Internal error. Error Message: Cannot read property 'show' of undefinedThis error is shown sporadically, especially when you Shift-Reload the whole page. SolutionI have a Vue.js Plugin to show “toast” messages (Vue.toasted). I currently use it for debugging purposes. Everything worked fine initially, as my code was executed after Vue was initialized and the whole [...]

By | August 8th, 2019|Development, Vue.js|Kommentare deaktiviert für Paho failure to subscribe

Getting POST requests to work with Axios, Kemal (crystal lang), vue.js

In picockpit.com, I am using AJAX requests to communicate with the backend for update operations. For instance,if you want to change the name of this Pi, you would select:which shows an inline form:how to show this inline form with vue.js is besides the point of this post (even though very interesting!)Clicking on Cancel will cancel [...]

By | August 6th, 2019|Crystal Language, Vue.js|Kommentare deaktiviert für Getting POST requests to work with Axios, Kemal (crystal lang), vue.js

VerneMQ MQTT connection lost (8): AMQJS0008I Socket closed. different mountpoints

In my setup, I am rewriting the mountpoints of clients from the ones set up by the listeners to individual mountpoints depending on client group.The idea behind this is perfect isolation of multi-tenancy on the server. Individual clients from different groups thus are not able to see each other, even when subscribing to “#” (everything). [...]

By | Juli 28th, 2019|VerneMQ|Kommentare deaktiviert für VerneMQ MQTT connection lost (8): AMQJS0008I Socket closed. different mountpoints

Shopify & Langify modify checkout link

Shopify checkout is multilingualThe shopify checkout is multilingual:The trick is to have a &locale=en or &locale=en at the end of the link:You can therefore create buttons, etc. which take your user to the checkout, under the links ofhttps://buyzero.de/checkout?locale=dehttps://buyzero.de/checkout?locale=enwhich will set the locale to the appropriate language.(replace buyzero.de by your domain).Shopify LiquidLiquid is the Shopify template [...]

By | Juli 21st, 2019|Development|Kommentare deaktiviert für Shopify & Langify modify checkout link

Debugging File upload / multipart upload and other HTTP requests

Sometimes you want to see the request as it is received by the server, without any handling / obscuring of the original request.For instance, to see whether different browsers handle file uploads differently. On the other hand, you do not want to write up your own mockup server, just to handle these requests, or install [...]

By | Juli 1st, 2019|Development|Kommentare deaktiviert für Debugging File upload / multipart upload and other HTTP requests

Changing the mountpoint on auth_on_register webhook for VerneMQ

It is possible to pass modifiers along with the “result”: “ok” return value of your webhook for VerneMQ.The official documentation of VerneMQ gives some examples for the syntax. changing the mountpointIt is also possible to change the mountpoint, however the client_id apparently has to be passed in as well!I have raised an issue with the [...]

By | Juni 9th, 2019|VerneMQ|Kommentare deaktiviert für Changing the mountpoint on auth_on_register webhook for VerneMQ

Maximimum length of credentials (username, password, clientid) in MQTT v3.1.1

The CONNECT packetThe MQTT CONNECT Control packet always contains a payload. It is the first packet, which the client must send to the server after the connection is established.It can only be sent once by the client, if a second CONNECT packet is sent, the server (broker) must process it as a protocol violation and [...]

By | Juni 9th, 2019|MQTT, VerneMQ|Kommentare deaktiviert für Maximimum length of credentials (username, password, clientid) in MQTT v3.1.1