Websockets are an exciting technology, allowing you to upgrade a HTTP connection to a long-running persistent binary connection, which you can use to send bi-directional messages.As an aside, the MQTT protocol can be transported using websockets – which is the only (?) way for a JavaScript client delivered by the website, for instance.In any case, [...]
The Paho documentation is unfortunately quite fragmented at the moment, and some links on Eclipse’s website do not work.Here are some working links (as of 05/2019):https://www.eclipse.org/paho/clients/js/https://www.eclipse.org/paho/files/jsdoc/index.htmlhttps://github.com/eclipse/paho.mqtt.javascriptAnd here’s a fantastic website by Steve:http://www.steves-internet-guide.com/using-javascript-mqtt-client-websockets/There is an important breaking change in the Paho namespace, where you will run into trouble using Steve’s code:“Previously the Client's Namepsace was Paho.MQTT, [...]
My goal / TLDRMy goal with this blog post is to explain how to set custom mountpoints for VerneMQ by modifying the shipped MongoDB auth Lua script (lua/auth/mongodb.lua).Setting a custom mountpoint is possible with VerneMQ not only by setting mountpoints manually for specific listeners (e.g. ports), but also programmatically during authorization in your scripts.I had [...]
When you extend your field definitions in the mongo_orm document classes, specifically with embedded documents, you might run into the following runtime (!) error:Exception: missing bson key: <name> (Exception)This is not an error in your code – your code is raising, because the database structure is not as it expects it to be!Here’s the sample [...]
IntroductionS.N.A.P. is a protocol for communication between several connected hosts. It provides:· addressing· flags· ack/nak request· error detection (different error detection methods available)It can be run over different media, including RS485. It is optimized for a small footprint (limited computing, memory resources), but scaleable depending upon your needs.Basically, if you want to connect several compute [...]
Abmessungen Raspberry PiEin Raspberry Pi 3B+ hat, als Vergleich, die Abmessungen: 85 mm x 56 mm für die Basisplatine. (USB & LAN, sowie andere Stecker ragen teilweise über die Platine hinaus). Hutschiene / DIN-SchieneHutschiene: TS35, U-förmiges Profil. Standarisierte Befestigungsschiene für Gehäuse, Racks, Schaltschränke, u.s.w. Sie wird vielfach in der Industrie eingesetzt. Einer der ersten Einsatzzwecke [...]
mongo_orm will automatically determine the name for your collection by using the Module and Class name, and appending an “s”.In cases where you want to name your collection, you can simply do this:class PapiTest < Mongo::ORM::Document collection_name "Buster" field test : String end get "/" do pt = PapiTest.new pt.test = "I want your sex" [...]
In some situations you would like to access the same computer / IP using different .local names.This is possible using the Avahi daemon. The following is written for Ubuntu 18.04 Bionic Beaver.Install Avahiapt install avahi-daemon avahi-utilsAvahi automatically adds your computer’s hostname to the .local Domain. For instance, my computer is called morpheus. Therefore it will [...]
If you want to host your own Raspbian repository, this article is for you.A Raspbian repository consists of a special directory structure on a webserver. The files, including the packages, are all static – therefore this repository could also simply be hosted on an Amazon S3 instance, for example.The sources.list entry in Raspbian/etc/apt/sources.listdeb http://raspbian.raspberrypi.org/raspbian/ stretch [...]