OPC-UA Interface

The OPC-UA interface is provided by the vnx.opc_ua.Server and vnx.opc_ua.Proxy modules.

They allow to access internal modules via OPC-UA method calls, as well as call methods on another OPC-UA server via a Lua Script for example.

Server

To enable the vnx.opc_ua.Server set the following config option:

cd ~/pilot
echo true > config/local/enable_opcua_server

The server will listen on the address opc.tcp://0.0.0.0:4840. The port 4840 is the default port for OPC-UA but you can also configure a different port.

The server module is called OPC_UA_Server, so it can be configured as usual by a config file config/local/OPC_UA_Server.json.

Exports

• Pilot modules and their methods are advertised by the server as OPC-UA services. The methods can be called according to the OPC-UA specification. The list of exported services is given by the config key export_services.
• Pilot topics are advertised as OPC-UA variables and continually updated whenever a new value is published. The list of exported topics is given by the config key export_topics.

To expand any of these lists, put a snippet like this in the configuration file:

{
        "export_services+": [
                "AnotherModule",
                ...
        ],
        "export_topics+": [
                "another.topic",
                ...
        ]
}

In order to replace any of the lists, omit the respective + character.

Security

The OPC-UA server supports encrypted communication. To enable it, you have to create or obtain a certificate and put the path in the configuration. You should also consider revisiting the key security_policies and adjust it to your needs.

{
        "certificate_file": "/some/path/to/server_cert.der",
        "private_key_file": "/some/path/to/server_key.der",
        "security_policies": [
                "NONE",
                "BASIC_256_SHA_256",
                "AES_128_SHA_256_RSA_OAEP"
        ]
}

Proxy

To run a vnx.opc_ua.Proxy which connects to another OPC-UA server create the following config file config/local/opcua_proxy_map:

[
        ["OPC_UA_Proxy_1", "opc.tcp://127.0.0.1:4840"],
        ...
]

The above proxy will be available unter the module name OPC_UA_Proxy_1, see Lua Script for examples on how to use it.

As usual, the module can be configured by a config file config/local/OPC_UA_Proxy_1.json.

Security

You can configure encrypted communication of the Proxy module. First obtain or generate a certificate and put the path in the configuration file. You should also consider chooosing a reasonable value for the key security_mode.

{
        "certificate_file": "/some/path/to/client_cert.der",
        "private_key_file": "/some/path/to/client_key.der",
        "security_mode": "SIGN_AND_ENCRYPT"
}

Certificates

To create self-signed certificates for the server and the proxy side, use the script provided by the open62541 project here as follows:

python create_self-signed.py -k 4096 -c server -u urn:open62541.server.application
python create_self-signed.py -k 4096 -c client -u urn:open62541.client.application

The -u switch sets the application URI that must match the one configured in the module. The values given here are the defaults.

Data Types

Primitive data types are directly mapped to their OPC-UA counter parts, such as int to INT32, float to FLOAT, etc. string is directly mapped to a OPC-UA STRING. Arrays of said types are directly mapped to OPC-UA arrays.

Anything else will be converted to JSON and transported via a LocalizedText object, with the locale set to JSON.