These are currently my working notes and resource links on the various technologies surrounding the internet of things wireless technologies.. Overview The Internet we as we currently know It consists of computers, tablets, and laptops connected to the Internet using either cable (Ethernet) or Wireless (Wi-Fi) Smart phones and tablets don’t have support for Ethernet. and use Wi-Fi as the main connection technology and mobile technologies ( 3G and 4G) when they’re not in the range of a WiFi connection. The IOT will consist of an array of new devices that are very different to tablets and PCs. The main characteristics
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MQTT Retained Messages Explained
Normally if a publisher publishes a message to a topic, and no one is subscribed to that topic the message is simply discarded by the broker. However the publisher can tell the broker to keep the last message on that topic by setting the retained message flag. This can be very useful, as for example, if you have sensor publishing its status only when changed e.g. Door sensor. What happens if a new subscriber subscribes to this status?
Continue readingMQTT Last Will and Testament Use and Examples
The last will and testament message is used to notify subscribers of an unexpected shut down of the publisher. The basic process is. The publisher tells the broker to notify all subscribers to a topic, using the last will message , in the event that the connection breaks If the broker detects a connection break it sends the last will message to all subscribers of that topic. 3. If the client disconnects using the disconnect message then no last will message is sent.
Continue readingMQTT Clean Sessions and QOS Examples
When a client connects to a broker it can connect using either a non persistent connection (clean session) or a persistent connection.. With a non persistent connection the broker doesn’t store any subscription information or undelivered messages for the client. This mode is ideal when the client only publishes messages. It can also connect as a durable client using a persistent connection.
Continue readingPython MQTT Client Connections– Working with Connections
The MQTT client uses a TCP/IP connection to the broker. Once the connection is established the client can send data to the broker, and the broker can send data to the client as required. You can consider a TCP/IP connection to be similar to a telephone connection. Once a telephone connection is established you can talk over it until one party hangs up.
Continue readingHow to Install The Mosquitto MQTT Broker on Windows
In this tutorial you will learn how to install the mosquitto MQTT broker (server) on Windows. See the installing Mosquitto on Linux tutorial for how to install on a local Linux server and also a cloud server (AWS).
Continue readingPaho Python MQTT Client – Publish With Examples
In this tutorial we will look at how you publish messages using the Paho Python MQTT client. We will use an example python script to publish messages, process the publish acknowledgements and examine QOS (quality of service) settings. Important Note feb 2024: The MQTT Python client has been upgraded to version 2.The code examples were written in version 1.5 . The change appears only to affect the callbacks which now have a properties field. This is for MQTTv5 compliance. You may need to add this to the callbacks in the examples. Tks matt. To publish a messages you use the
Continue readingUnderstanding The Domain Name Structure
To understand the domain name structure you really need to understand the problem the structure was meant to solve. The Domain Name Structure and Domain Name System were developed to organise and find the IP addresses of Computers on large distributed networks.
Continue readingUnderstanding HTTP Basics
HTTP stands for hypertext transfer protocol and is used to transfer data across the Web. It is a critical protocol for web developers to understand and because of it widespread use it is also used in transferring data and commands in IOT applications. The first version of the protocol had only one method, namely GET, which would request a page from a server. The response from the server was always an HTML page.- Wiki To give you an idea of how simple the HTTP protocol started out take a look at the Original specification which was only 1 page.
Continue readingHow to Use Nslookup – Beginners Guide
nslookup is a network administration command-line tool available for many computer operating systems. It is used for querying the Domain Name System (DNS) to obtain domain name or IP address mapping information .- Wiki
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