MQTT Bridge

Message broker connection for IoT and telemetry communication.

Overview

The MQTT Bridge provides MQTT (Message Queuing Telemetry Transport) connectivity for OpenEMS Edge systems. It enables lightweight publish-subscribe communication with MQTT brokers, supporting MQTT versions 3.1, 3.1.1, and 5.0 via Eclipse Paho client. This bridge is ideal for IoT integration, remote monitoring, telemetry collection, and inter-system communication in scalable, distributed architectures.

MQTT is a perfect alternative to direct device protocols when devices support broker-based communication or when working with cloud platforms, IoT hubs, and distributed systems.

Components

Bridge MQTT

Name: Bridge MQTT

Factory-PID: Bridge.Mqtt

Purpose: MQTT broker connection and message routing for OpenEMS components.

Configuration:

  • id (String): Unique bridge identifier; default: "mqtt0"

  • alias (String): Human-readable name; default: same as id

  • enabled (Boolean): Enable/disable this component; default: true

  • mqttVersion (MqttVersion): Protocol version (V3_1, V3_1_1, V5_0); default: V3_1_1

Broker Connection

  • host (String): MQTT broker hostname or IP; default: "localhost"

  • port (Integer): MQTT broker port; default: 1883 (use 8883 for TLS)

  • secureConnect (Boolean): Use SSL/TLS encryption; default: false

Authentication

  • username (String): Broker authentication username (optional)

  • password (String): Broker authentication password (optional)

  • clientId (String): Unique client identifier; if empty, auto-generated

Session Management

  • cleanSession (Boolean): Start with clean session (no persistent subscriptions); default: true

  • keepAliveInterval (Integer): Keep-alive interval in seconds (0=disabled); default: 60

  • connectionTimeout (Integer): Connection timeout in seconds; default: 30

Reconnection

  • autoReconnect (Boolean): Automatically reconnect on failure; default: true

  • reconnectDelayMs (Integer): Initial reconnect delay (ms); default: 1000

  • maxReconnectDelayMs (Integer): Maximum reconnect delay (ms); default: 30000

Last Will & Testament (LWT)

  • lwtTopic (String): Topic for LWT message (optional)

  • lwtMessage (String): Message to send when connection lost

  • lwtQos (QoS): QoS level for LWT (AT_MOST_ONCE, AT_LEAST_ONCE, EXACTLY_ONCE); default: AT_LEAST_ONCE

  • lwtRetained (Boolean): Retain LWT message; default: false

SSL/TLS Certificates

  • trustStorePath (String): Path to trust store file for server verification (optional)

  • trustStorePassword (String): Trust store password (optional)

  • keyStorePath (String): Path to client certificate key store (optional)

  • keyStorePassword (String): Key store password (optional)

Debugging

  • debugMode (Boolean): Enable debug logging for MQTT communication; default: false

Supported MQTT Versions

MQTT 3.1 & 3.1.1

  • Stable, widely supported

  • Good for legacy systems and public brokers

  • Default for most installations

MQTT 5.0

  • Enhanced features (message properties, improved error handling)

  • Better for high-performance scenarios

  • Requires broker supporting MQTT 5.0

Source Code