MQTT Protocol Overview

MQTT Overview

• MQTT (Message Queuing Telemetry Transport) is a lightweight publication/subscription messaging protocol, widely adopted in the Industrial Internet of Things.
• Designed for battery-powered devices, MQTT provides low power consumption and is suitable for unreliable communication networks.

Architecture and Components

• MQTT is based on a subscriber, publisher, and broker model.
• The publisher collects data and sends information to subscribers via the broker (mediation layer).
• The broker ensures security by cross-checking the authorization of publishers and subscribers.

Quality of Service (QoS)

• MQTT offers three QoS modes:
  • QoS0 (At most once): Fastest mode, but least reliable, with no confirmation of receipt.
  • QoS1 (At least once): Ensures message delivery at least once, but duplicates may occur.
  • QoS2 (Exactly once): Most reliable mode, but most bandwidth-consuming, with duplicate control.

IoT Applications

• MQTT is widely used in IoT devices, such as electric meters, vehicles, detectors, and industrial/sanitary equipment, due to its:
  • Low bandwidth use
  • Operation over wireless networks
  • Low energy consumption
  • Good reliability (if necessary)
  • Little processing and memory resources

Limitations and Variants

• MQTT can be problematic for very restrictive devices due to TCP transmission and long topic names.
• The MQTT-SN variant uses UDP and supports topic name indexing, addressing these limitations.

MQTT Characteristics

• Lightweight publish and subscribe system
• Designed for constrained devices with low-bandwidth
• Ideal for Internet of Things applications
• Enables easy communication between multiple devices

MQTT Basic Concepts

• Publish/Subscribe: Devices can publish messages on topics or subscribe to receive messages
• Messages: Information exchanged between devices, such as commands or data
• Topics: Represented by strings separated by forward slashes, specifying message interest or publication