EtherNet/IP Emulator (Python)

ethernetip-emulator is a high level binary communications framework built around cpppo (pronounced ‘c’3*’p’‘o’ in Python) that exposes a set of tags and allows for the programatic execution .

Architecture

.
├───example
│   ├───basic_datatypes
│   │   └─── *.py
│   ├───mfg_line
│   │   └─── *.py
│   ├───orange_pi
│   │   └─── *.py
│   └───raspberry_pi
│       └─── *.py
├───src
│   └───ethernetip_emulator
│       ├───client
│       ├───server
│       │   ├───datatypes
│       │   │   ├───templates
│       │   │   │   └─── *.py
│       │   │   └─── *.py
│       │   └─── *.py
│       └─── *.py
└───tests
    └───server
        ├───datatypes
        │   ├───mock
        │   │   └─── test_*.py
        │   ├───templates
        │   │   └─── test_*.py
        │   └─── test_*.py
        └─── test_*.py
        

Requirements

• Python 3.10+
• cpppo (for Ethernet/IP attribute/device behavior)
• black | Development Dependency (for code formatting)
• coverage | Developer Dependency (for coverage reporting)
• RPi.GPIO or OPi.GPIO | Optional Dependency (for gpio i/o)

Getting Started

pip install ethernetip-emulator

A minimal project needs three files:

# __main__.py
from ethernetip_emulator.server.device import AttributeDevice, apidict, device_controller
from ethernetip_emulator.server.tag_specs import tag_registry
import tags    # registers all tags (can also just be imported in __init__.py)
import actions # registers all listeners (can also just be imported in __init__.py)

if __name__ == "__main__":
    server_control = apidict(timeout=1.0)
    AttributeDevice.set_server_control(server_control)

    with AttributeDevice._actions.bind(AttributeDevice):
        device_controller(
            argv=tag_registry.build_argv(base_args=["--print"]),
            attribute_class=AttributeDevice,
            server={"control": server_control},
        )

Guides

Core

Datatypes

Typical Workflow

┌─────────────────────────────────────────────────────┐
│                    Your Project                     │
│                                                     │
│  tags.py ──────► tag_registry                       │
│                      │                              │
│                       ▼                             │
│  datatypes.py ─► actions.datatype                   │
│                      │                              │
│                       ▼                             │
│  __main__.py ──► device_controller                  │
│                      │                              │
│                       ▼                             │
│              AttributeDevice                        │
│           (intercepts PLC writes)                   │
│                      │                              │
│                       ▼                             │
│  actions.py ──► on_change listeners                 │
│                      │                              │
│                       ▼                             │
│              actions.<type>.set_val / get_val       │
└─────────────────────────────────────────────────────┘

1. Tags are declared once at import time via @tag_registry.register.
2. Custom Datatypes can be declared once at import time via @actions.datatype. Although this is completely optional if you like the built-in datatypes
3. device_controller builds the tag list and starts the EtherNet/IP server.
4. AttributeDevice intercepts every PLC write and fires the matching on_change listeners.
5. Listeners use actions.<type> helpers to read state, write back to tags, or trigger application logic.

Project Layout Convention

your_project/
├── __main__.py          # server entrypoint
├── tags.py              # tag definitions
├── actions.py           # on_change handlers
└── datatypes/           # optional: custom datatype classes
    ├── __init__.py
    └── mytype.py

For larger projects, split tags and actions into sub-modules and import them from a top-level __init__.py so all registrations are triggered before the server starts.

Supporting the Development of EtherNet/IP Emulator

EtherNet/IP Emulator's development depends on your contributions. Right now it is just me working on this, so any contributions are welcome!

License

Copyright 2026 Merck KGaA, Darmstadt, Germany and/or its affiliates. All rights reserved.