---
title: MQTT collector
slug: reference/mqtt-collector
docTags: 
createdAt: 2025-09-09T09:41:42.339Z
---

## Basic settings

The collector settings are used to connect to the MQTT broker.

### MqttURL

**Description**: The connection URL for the MQTT broker.
**Required**: yes
**Example**: tcp\://localhost:1883

### ClientCertificate

**Description**: Use a client certificate. This is a toggle, not a place to paste a certificate: when enabled the collector reads `cert.pem` and `key.pem` from the `certificates` directory under its base path, and generates a self-signed pair there if either file is missing.
**Required**: no
**Default**: false
**Options**: false | true

### Username

**Description**: Username
**Required**: no

### Password

**Description**: Password
**Required**: no

### Topics

**Description**: Comma separated list of topics to subscribe to. (Wildcards are allowed)
**Required**: yes

### QOS

**Description**: QOS with which to subscribe.
**Required**: yes
**Default**: 1
**Options**: 0 | 1 | 2

### KeepAliveSecs

**Description**: The keep alive period in seconds, before which the client sends a ping to the mqtt broker (default is 30 seconds). On no response received, the connection is closed.
**Required**: no
**Default**: 30

### PersistentSession

**Description**: If the session is persistent, the broker will store the session information and deliver messages to the client while it is disconnected.
**Required**: no
**Default**: false

:::hint{type="warning"}
A persistent session survives a crash, a network drop or a restart, but not a pause. Pausing the collector clears its session on the broker, which discards everything queued for it, and resuming clears it again before reconnecting. Do not pause a collector expecting the broker to hold its data.
:::

## Advanced settings

### CACertificate

**Description**: PEM encoded CA certificate or chain used to verify the broker's TLS certificate. Paste the full certificate, including the BEGIN and END CERTIFICATE lines. Leave empty to use the system trust store.
**Required**: no

### InsecureSkipVerify

**Description**: When enabled, the broker's TLS certificate is not verified. Only use this for testing, or with a broker whose certificate is not RFC 5280 compliant.
**Required**: no
**Default**: false

### PingTimeout

**Description**: The time in seconds to wait for a response to a ping before the connection is regarded as lost.
**Required**: no
**Default**: 30

### WriteTimeout

**Description**: The time in seconds a publish may take before it returns a timeout error. 0 means it never times out.
**Required**: no
**Default**: 0

### ConnectionTimeout

**Description**: The time in seconds to wait when opening a connection to the broker.
**Required**: no
**Default**: 30

### MaxReconnectInterval

**Description**: The maximum time **in minutes** to wait between reconnection attempts after a disconnection.
**Required**: no
**Default**: 10

### ConnectRetryInterval

**Description**: The time in seconds to wait between attempts while initially connecting.
**Required**: no
**Default**: 30

### HandleMessagesAsync

**Description**: When enabled, incoming messages are handled asynchronously.
**Required**: no
**Default**: true

## Configuration

This guide provides comprehensive instructions for setting up and configuring the MQTT collector for Factry Historian. It includes installation steps, connection setup, and best practices for secure and reliable data transmission.

### Collector Installation

To install the MQTT collector, follow the steps outlined in the Collector Installation Guide .

### Connecting the MQTT Collector to a Broker

To connect the MQTT collector to your broker, ensure the following configurations are properly set up:

**Authentication**

- Provide the **username** and **password** required for broker authentication.

**Secure Communication (TLS)**

- Use a **CA certificate** to validate the broker’s identity.
- For mutual TLS, enable `ClientCertificate` and place `cert.pem` and `key.pem` in the `certificates` directory under the collector's base path. If either file is missing the collector generates a self-signed pair, which the broker has to trust.

:::hint{type="info"}
While TLS is optional, it is highly recommended for secure environments to ensure encrypted communication and prevent unauthorized access.
:::

### Quality of Service (QoS)

MQTT supports three levels of **Quality of Service** (QoS), each offering different guarantees for message delivery:

| Level | Description   | Guarantee                                       | Use Case                            |
| ----- | ------------- | ----------------------------------------------- | ----------------------------------- |
| QoS 0 | At most once  | No guarantee of delivery                        | Non-critical data                   |
| QoS 1 | At least once | Message delivered at least once (may duplicate) | Recommended for most industrial use |
| QoS 2 | Exactly once  | Message delivered **exactly once**              | Critical data, higher overhead      |

:::hint{type="info"}
**Recommendation:** Use QoS 1 or QoS 2 to ensure reliable delivery of measurement data.
:::

### Topics

MQTT **topics** are used to route messages. The collector subscribes to specific topics to receive data.

- Topics act as **filters**: the collector only processes messages from subscribed topics.
- Measurement configurations can only extract data from these subscribed topics.

**Wildcards in Topics**

MQTT supports wildcards for flexible topic subscriptions:

**Single-Level Wildcard:** `+`

Matches **exactly one level** of a topic.

**Example**:
`factory/+/temperature` matches:

- `factory/machine1/temperature`
- `factory/machine2/temperature`

**Multi-Level Wildcard: **`#`

Matches **multiple levels** (including zero) and must be the **last character** in the topic.

**Example**:
`factory/#` matches:

- `factory/machine1`
- `factory/machine1/temperature`
- `factory/machine2/status/online`

For more information and best practices, refer to: [MQTT Topics Best Practices – HiveMQ](https://www.hivemq.com/blog/mqtt-essentials-part-5-mqtt-topics-best-practices/)

## MQTT messages

There are multiple types of messages that can be processed via MQTT: 

- JSON messages: see [JSON Settings](docId\:Wzx5O0pO00YfahZxqiXzw) 
- Sparkplug B messages: see [Sparkplug B Settings](docId\:ey5TGFrnf4egfqZemBzXO)