MQTT Broker

Overview

Mosquitto is the central MQTT server that handles all messages between the iBOAR modules (services).

Each service acts as a client that can publish or subscribe to topics.

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Basic MQTT Concepts

Clients

• Can publish messages or subscribe to topics.

Topics

• Topics are like communication channels.
• Subscribing to a topic means you receive all messages sent to that channel.

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QoS (Quality of Service) Levels

Level	Description	Example Use
0	Fire and forget (no confirmation). Fast but not guaranteed.	Lidar Controller data updates
1	Delivered at least once. May duplicate messages.	Remote control commands
2	Guaranteed exactly once. Slowest but safest.	Critical commands (e.g., startAutonomousMapping)

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Topic Structure

• Format: topic/subTopic/...
• Wildcards:
  • topic/#: Subscribe to all subtopics.
  • +/subTopic: Subscribe to a specific subtopic under any first-level topic.

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🛠️ Commands

Action	Command
Start Broker	sudo systemctl start mosquitto
Stop Broker	sudo systemctl stop mosquitto
Subscribe to Topic	mosquitto_sub -h localhost -t "example/topic"
Publish to Topic	mosquitto_pub -h localhost -t "example/topic" -m "Test message"