---
title: OPC
slug: sdk/opc
docTags: 
createdAt: 2026-05-08T21:20:11.062Z
---

The OPC UA module manages the OPC UA server on Litmus Edge: service configuration, security policies, and the node hierarchy.

## Imports

```python
from litmussdk import opc
```

All functions are accessible directly from the `opc` namespace.

***

## Service Management

### Start / Stop

```python
opc.start_stop_opc(start=True)
opc.start_stop_opc(start=False)
```

### Service Configuration

```python
# Get current config
config = opc.get_service_config()
# {host, port, nodesUnderRoot, ...}

# Update config
opc.change_service_config(
    host="0.0.0.0",
    port=4840,
    nodes_under_root=True,
)
```

### Security and Authentication

```python
# Get current settings
settings = opc.get_security_and_auth_settings()

# Update policies
opc.change_security_and_auth_settings(
    enabled_security_modes=["None", "Sign", "SignAndEncrypt"],
    enabled_security_policies=["Basic256Sha256", "Aes128_Sha256_RsaOaep"],
    enabled_auth_modes=["Anonymous", "Password"],
)
```

Valid `enabled_security_modes`: `"None"`, `"Sign"`, `"SignAndEncrypt"`

Valid `enabled_security_policies`: `"Basic256Sha256"`, `"Basic256"`, `"Basic128Rsa15"`, `"Aes128_Sha256_RsaOaep"`, `"Aes256_Sha256_RsaPss"`

Valid `enabled_auth_modes`: `"Anonymous"`, `"Certificate"`, `"Password"`

### Certificates and Metrics

```python
certs = opc.get_server_certificates()  # dict
metrics = opc.get_server_metrics()     # dict
```

***

## Hierarchy

The OPC hierarchy is a tree of **Folder**, **Device**, and **Tag** nodes.

### Viewing the Hierarchy

```python
# Root node
root = opc.get_root_node()

# Specific nodes by path
nodes = opc.get_node_by_paths(["edgedevice/MyFolder", "edgedevice/MyFolder/MyDevice"])

# Export entire hierarchy as JSON
hierarchy = opc.export_as_json()
```

### Adding Nodes

```python
# Folder
folder_id = opc.add_node_folder(
    name="MyFolder",
    parent_id="edgedevice",
    worker_node_id_mode="hierarchical",  # or "fixed"
)

# Device (under a folder)
device_id = opc.add_node_device(
    name="MyDevice",
    parent_id=folder_id,
)

# Tag (under a device)
tag = opc.add_node_tag(
    name="Pressure",
    parent_id=device_id,
    data_type="uint32",
    topic_name="plant/pump/01/pressure",
)
```

`worker_node_id_mode`:

- `"hierarchical"` (default): node ID is auto-generated from the tree position
- `"fixed"`: provide an explicit `worker_node_id`

### Updating a Node

All fields must be specified:

```python
opc.update_node_by_id(
    node_id=folder_id,
    parent_id="edgedevice",
    name="RenamedFolder",
    node_type="FOLDER",
    worker_node_id="edgedevice.RenamedFolder",
    worker_node_id_mode="fixed",
)
```

For TAG nodes, also pass `data_type` and `topic_name`.

### Removing a Node

```python
opc.remove_single_node(node_id)
```

### Reset Hierarchy

```python
opc.reset_manual_hierarchy()    # removes manually created nodes
opc.reset_imported_hierarchy()  # removes auto-imported nodes
opc.reset_all_hierarchy()       # removes everything
```

### Import from DeviceHub

Auto-import all DeviceHub tags as OPC nodes:

```python
opc.import_all_dh_tags()
```

### Import / Export JSON

```python
import json

# Export
hierarchy = opc.export_as_json()
with open("opc_hierarchy.json", "w") as f:
    json.dump(hierarchy, f)

# Import (replaces current hierarchy)
with open("opc_hierarchy.json") as f:
    opc.import_json(json.load(f))
```

***

## License

Copyright (c) Litmus Automation Inc.