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MQTT Basics
What's MQTT All About?
MQTT stands as the quintessential protocol for messaging and data interchange within the realm of the Internet of Things. Operating on a publish/subscribe framework, this protocol furnishes a scalable and economical means of linking devices across the expanse of the Internet. With the ability to transmit data almost instantaneously and ensure delivery, MQTT caters aptly to the demands of IoT devices, characterized by their lightweight nature facilitating cost-effective communication.
Who Engages with MQTT?
A plethora of major corporations, particularly in the automotive, industry 4.0, transportation, and entertainment spheres, leverage MQTT for data interchange between constrained devices and server applications. Renowned for its minimal bandwidth requisites, adeptness in handling unreliable networks, and ease of implementation for developers, MQTT emerges as the prime choice for facilitating machine-to-machine (M2M) communication.
How Does MQTT Operate?
MQTT adheres steadfastly to the Publish/Subscribe paradigm, facilitating seamless communication between message senders (Publishers) and receivers (Subscribers) through designated topics, while maintaining decoupling. The intermediary responsible for orchestrating this communication is the broker, tasked with filtering incoming messages and dispatching them accurately to subscribers. In this setup, clients need not actively retrieve information; rather, the broker proactively pushes new information to them.
Unveiling the MQTT Client
Any device, be it a microcontroller or a fully-fledged server, equipped with an MQTT library and connected to an MQTT broker via a network, qualifies as an MQTT client. Each such client holds the capability to function as both publisher and/or subscriber.
The Role of an MQTT Broker
At the core of any MQTT deployment lies the MQTT broker, capable of handling myriad concurrently connected MQTT clients based on the specific implementation. This pivotal component is entrusted with receiving, filtering, identifying interested parties, and disseminating messages to subscribed clients.
Delving into MQTT Topics
The crux of communication in MQTT hinges on the topic-centric approach. An MQTT topic, comprising a UTF-8 string, serves as the conduit through which the broker sieves messages for each connected client. Clients must subscribe to relevant topics to receive messages, with topics potentially encompassing multiple levels, demarcated by slashes (Topic Level Separator).
Ensuring MQTT's Security
Designed with security paramount, MQTT offers robust communication avenues, incorporating extensive device authentication and authorization mechanisms. The underlying TCP/IP transport protocol can further fortify security via TLS encryption.
MQTT's Open Source Nature
MQTT stands as an open protocol, standardized by OASIS and ISO (ISO/IEC 20922:2016), fostering a collaborative and inclusive ecosystem.
Integration with WebSockets
Through adept broker implementations supporting native WebSockets, MQTT can seamlessly operate with its entire feature set via WebSockets, furnishing a bidirectional, ordered, and lossless communication conduit via TCP.
TCP: MQTT's Transport Protocol of Choice
Utilizing TCP, MQTT eschews UDP due to its inherent ordering constraints, rendering MQTT over UDP an impractical endeavor.
For an exhaustive elucidation, refer to the MQTT Q&A Video: https://youtu.be/zvthFJ-sigA?si=5jlaJcVsKZSelRsx
Necessity of Internet Connectivity for MQTT
Indubitably, to initiate or receive messages, an MQTT client must establish a TCP connection with the broker. Nonetheless, MQTT comes equipped with features tailored to surmount challenges posed by erratic network connections, such as the broker buffering incoming messages for disconnected clients.