Mosquitto
Eclipse Mosquitto is an open-source MQTT broker used for publish/subscribe communication between systems, applications, sensors and industrial equipment. The platform is designed for lightweight, scalable and efficient data communication, particularly within the Industrial Internet of Things, Edge Computing and Industrial Automation.
Mosquitto plays an important role within modern IT OT Convergence architectures because it can reliably distribute OT data between field equipment, edge platforms, cloud environments and analytics systems.
Frequently used applications:
- IIoT platforms
- Sensor communication
- Machine monitoring
- SCADA integration
- Edge gateways
- Unified Namespace architectures
- Real-time event streaming
Mosquitto is often combined with:
⚙️ How Mosquitto works
Mosquitto functions as a central message broker within an MQTT Architecture.
Basic operation:
- A publisher sends data to a topic
- Mosquitto receives the message
- Subscribers receive messages on the topics they have subscribed to
This produces a decoupled communication architecture.
Example:
Factory/Line1/Temperature
A temperature sensor publishes data to this topic, after which multiple systems can consume the data:
Mosquitto handles:
- Message routing
- Session management
- Authentication
- QoS handling
- Persistence
🏭 Applications in industrial automation
Within Industrial Automation, Mosquitto is used for efficient distribution of OT data.
Machine monitoring
- Temperature measurements
- Vibration
- Status information
- Energy consumption
Edge computing
- Local data buffering
- Protocol conversion
- Event streaming
Unified Namespace
Mosquitto is widely used as a central broker within a Unified Namespace.
In this model, all OT Assets publish their data to a central namespace.
SCADA integration
- Alarm distribution
- Process values
- Historical data
- Real-time events
Smart manufacturing
- Production tracking
- MES integration
- Asset intelligence
🧠 MQTT publish/subscribe model
Mosquitto uses the publish/subscribe model from MQTT.
Key components:
| Component | Function |
|---|---|
| Publisher | Sends data |
| Broker | Processes messages |
| Subscriber | Receives data |
| Topic | Communication channel |
Advantages:
- Low network load
- Asynchronous communication
- Scalability
- Loose coupling
- Low Latency
This makes MQTT particularly well suited to industrial networks with limited bandwidth.
📡 MQTT Quality of Service
Mosquitto supports MQTT QoS levels.
| QoS | Description |
|---|---|
| QoS 0 | At most once |
| QoS 1 | At least once |
| QoS 2 | Exactly once |
Within OT systems, QoS is chosen based on:
- Reliability
- Latency
- Network capacity
- Criticality
For critical alarms, QoS 1 or QoS 2 is often used.
🌐 Architecture in OT environments
Mosquitto is usually positioned between OT assets and higher IT systems.
Typical architecture:
| Layer | Component |
|---|---|
| Field layer | Sensor, PLC |
| Edge layer | MQTT gateways |
| Broker layer | Mosquitto |
| Analytics | Grafana, InfluxDB |
| Enterprise | MES, ERP, cloud |
Frequently used integrations:
- PLC → MQTT Gateway → Mosquitto
- OPC UA → MQTT bridge
- Edge Device → Mosquitto → Cloud
In this setup, Mosquitto functions as a central event bus.
🔄 Retained messages and persistence
Mosquitto supports retained messages.
A retained message remains available for new subscribers.
Applications:
- Last known machine status
- Configuration values
- Alarm status
- Production parameters
In addition, Mosquitto supports:
- Persistent sessions
- Offline buffering
- Message queues
This increases reliability within unstable networks.
⚡ Performance and Scalability
Mosquitto is designed as a lightweight broker with low resource consumption.
Key properties:
- Low CPU load
- Low memory consumption
- High message throughput
- Low latency
This makes Mosquitto suitable for:
Performance issues often arise from:
- Large retained datasets
- High QoS levels
- Excessive topic structures
- Many concurrent clients
🧩 Topic structures in OT
Good topic structures are essential.
Frequently used hierarchies:
Factory/Line/Machine/Sensor
Example:
Plant1/Line2/Robot5/Temperature
Best practices:
- Consistent naming
- Logical hierarchy
- Limited topic depth
- Separation between OT and IT data
Within Unified Namespace architectures, topic structure is an important Governance component.
🔐 Cybersecurity of Mosquitto
Because Mosquitto often handles critical OT data, security is essential.
Key risks:
| Risk | Consequence |
|---|---|
| Unauthorised publish | Process manipulation |
| Topic spoofing | Incorrect data |
| Weak authentication | Unauthorised access |
| Unencrypted connections | Data theft |
Key security controls:
Mosquitto supports:
- Username/password authentication
- Certificate authentication
- ACL rules
- TLS encryption
Within OT environments, Mosquitto is usually placed within a segmented IDMZ or edge zone.
🚨 Availability and reliability
In industrial environments, message distribution must remain reliable.
Key design choices:
- Broker Redundancy
- High Availability
- Persistent storage
- Edge buffering
- Monitoring
Broker failure can lead to:
- Loss of Telemetry
- Incomplete dashboards
- Missed alarms
- Halted analytics
For this reason, monitoring of Mosquitto itself is often integrated into Monitoring platforms.
📈 Monitoring Mosquitto
Key metrics:
| Metric | Meaning |
|---|---|
| Connected clients | Active connections |
| Message throughput | Messages per second |
| Queue depth | Queue length |
| Dropped messages | Loss detection |
| CPU usage | Broker load |
Integrations exist with:
This produces real-time observability of the MQTT infrastructure.
☁️ Cloud, edge and hybrid architectures
Mosquitto supports multiple deployment models.
Edge deployment
Widely used for:
- Low latency
- Local buffering
- Protocol conversion
- Offline operation
Central OT broker
Used for:
- Plant-wide data distribution
- Unified Namespace
- SCADA integration
Cloud integration
Mosquitto can distribute data to:
- Azure IoT
- AWS IoT
- Cloud analytics platforms
Within critical infrastructures, cloud integration is often restricted due to Security and Compliance requirements.
🔄 Mosquitto versus traditional OT communication
| Property | Mosquitto/MQTT | Traditional fieldbus |
|---|---|---|
| Architecture | Publish/subscribe | Point-to-point |
| Scalability | High | Limited |
| Bandwidth usage | Efficient | Variable |
| Cloud integration | Strong | Limited |
| Real-time determinism | Limited | Strong |
| OT-native | Partially | Yes |
Mosquitto generally does not replace real-time Fieldbuses, but acts as a complementary data distribution layer.
🏗️ Mosquitto in IT/OT convergence
Within IT OT Convergence, Mosquitto plays a central role as an event-driven communication layer between OT Assets and IT platforms.
Applications:
- Real-time data streaming
- Asset intelligence
- Unified Namespace
- Predictive Maintenance
- Digital twins
- Cloud analytics
Mosquitto supports modern OT initiatives such as:
It thereby forms an important foundation for scalable industrial data architectures.