Integrations

Allen-Bradley (EtherNet/IP) to MQTT, without a script.

Read ControlLogix, CompactLogix or Micro800 tags by name with MaestroHub's EtherNet/IP connector, including whole UDTs, and publish them to your MQTT broker on topics from the plant model with unit and quality.

The flow

One value, from the machine to MQTT. Illustrative.

Allen-Bradley (EtherNet/IP)PLC protocolProgram:Line2.Filler.Speed

MaestroHub

Filler 2 speed · 412 bpm · Good

named, unit, quality
origin stamped
buffered on disk

MQTTmessage brokerplant/line2/filler2/speed

Why do it with MaestroHub

More than a pipe from Allen-Bradley (EtherNet/IP) to MQTT.

Tags by name, UDTs whole

Read structures as they are in the controller, without unpacking them by hand.

Batch reads that stay honest

Many tags in one call, each with its own result, so one bad tag never hides the others.

Mixed plants, one broker

Allen-Bradley lines publish next to Siemens and Modbus equipment in the same structure.

What lands in MQTT

An example. You choose the fields in the pipeline.

topic	value	unit	quality	ts
plant/line2/filler2/speed	412	bpm	good	2026-10-03T06:00:01Z

Set it up in three steps

1
Connect Allen-Bradley (EtherNet/IP)
Add the controller, list its tags with their types and pick the ones you need; a batch read fetches many in one call.
2
Give the values meaning
Map each value to a topic in the namespace with its name, unit and schema. Quality and origin are stamped on every value.
3
Deliver to MQTT
Add an MQTT publish output with a topic template, so every value lands on a clean, predictable topic.

Before you start

What each side needs, from the connector documentation.

Allen-Bradley (EtherNet/IP)

MaestroHub must reach the controller on TCP port 44818. For a ControlLogix, use the Ethernet module's address, for example a 1756-EN2T.
The controller family (Logix or Micro800) and, for Logix, the CPU slot: 0 for a CompactLogix, the physical slot for a ControlLogix.
Tags whose External Access in Studio 5000 is not None. Read Only tags and constants refuse writes.
The tag names from the controller program, found with Browse Tags or a Studio 5000 .L5X export.

Example settings

PLC Host: 192.168.1.10
Port: 44818
Controller Family: Logix
PLC Slot: 0
Timeout (ms): 5000
Keep-Alive Interval (ms): 10000

Allen-Bradley (EtherNet/IP) connector documentation

MQTT

A reachable MQTT broker: hostname, port (typically 1883 plain, 8883 for TLS) and protocol tcp, ssl, ws or wss.
Broker credentials if the broker requires them. A password needs a username.
For verified TLS or mutual TLS: the CA certificate, client certificate and private key in PEM format.

Example settings

Protocol: ssl
Broker Hostname: broker.example.com
Port: 8883
MQTT Version: 3.1.1
Client ID: <your-client-id>
Keep Alive (sec): 60

MQTT connector documentation

Things to know

Pitfalls and limits the documentation calls out, so they don't surprise you on site.

Allen-Bradley (EtherNet/IP)

The data type must match the tag, or the read is refused with the tag's real type. Use auto when you do not know the type.
Program-scoped tags need the Program:<Program>.<Tag> prefix. Without it the controller answers CIP status 0x04, not found.
A Micro800 accepts up to 16 connections at a time and exposes only global variables. Keep the number of MaestroHub connections and other clients to one controller small.

Limits

SLC 500, MicroLogix and PLC-5 (PCCC controllers) are not supported. Cyclic class 1 I/O connections are not used.
Writing a single bit of an integer or a whole structure (UDT) is not supported: write the integer or the members. A STRING write stores up to 82 characters.

MQTT

Plain ws cannot use TLS. Use wss for TLS over WebSocket.
The certificate fields appear only when TLS is on and certificate verification is not skipped.
On MQTT 5.0, write a shared subscription in the topic filter to load-balance across clients: $share/<group>/<topic>.

Limits

Reconnection, subscription recovery and message acknowledgement are handled by the platform and cannot be configured on the connection.

What teams use it for

Unified namespace on Rockwell lines

Logix controllers feeding the broker the whole plant uses.

OEE from PLC states

Run, idle and fault states per machine.

Pick tags offline

Load a Studio 5000 export to choose tags before you are on site.

Ways to connect Allen-Bradley (EtherNet/IP) to MQTT

In general terms. Check any specific product for its own details.

Compare a custom script, a flow tool, a cloud vendor's edge service and MaestroHub

Swipe sideways to see every column

	A custom script	A flow tool	A cloud vendor's edge service	MaestroHub
Talks Allen-Bradley (EtherNet/IP)	A library you choose	Community plug-ins	Depends on the vendor	Built in, one of 90+ connectors
Names, units and schema	You write it	You build it	Partly, in the vendor's model	One governed namespace
Quality on every value	You write it	You build it	Depends on the vendor	Built in, carried through calculations
Where each value came from	You write it	You build it	Depends on the vendor	Stamped on every value
Survives a network outage	You build it	You build it	Usually, to that vendor's cloud	On disk, per destination, in order
Several destinations at once	One script each	Yes, flow by flow	Mostly that vendor's cloud	Any mix, each with its own buffer
Permissions and audit	You build it	You build it	Cloud account permissions	Roles, single sign-on, audit trail
AI agents can use the data	You build it	You build it	Depends on the vendor	Through the MCP server

Questions

How do I publish Allen-Bradley ControlLogix tags to MQTT?

Do I need to write code to connect Allen-Bradley (EtherNet/IP) to MQTT?

No. You configure the Allen-Bradley (EtherNet/IP) connection and the MQTT output in MaestroHub and join them with a pipeline. Transformations can be added where you need them.

Where does MaestroHub run for this?

On your own infrastructure next to the machines: an edge box, a virtual machine or Kubernetes. Nothing has to leave your network.

Why not just write a script for Allen-Bradley (EtherNet/IP) to MQTT?

A script works on day one. The cost comes later: decoding and naming values, handling bad quality, buffering through outages, keeping credentials safe, and doing it again for the next machine and the next destination. MaestroHub does those once, for every connector.

What else can Allen-Bradley (EtherNet/IP) data go to?

More than 90 connectors are included in every edition, among them historians, databases, cloud warehouses, message brokers and business systems, so the same values can feed several destinations at once.

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