{"id":11371,"date":"2024-12-10T20:30:56","date_gmt":"2024-12-10T19:30:56","guid":{"rendered":"https:\/\/www.basyskom.de\/?p=11371"},"modified":"2024-12-11T11:57:53","modified_gmt":"2024-12-11T10:57:53","slug":"revisiting-nodeopcua","status":"publish","type":"post","link":"https:\/\/www.basyskom.de\/en\/revisiting-nodeopcua\/","title":{"rendered":"Revisiting NodeOPCUA"},"content":{"rendered":"\t\t
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Introducing NodeOPCUA<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The NodeOPCUA<\/a> library is a very mature OPC UA implementation for TypeScript\/JavaScript on the Node.js platform. Since the initial release eleven years ago, it has been continuously updated and extended by the main developer and various external contributors. Read this article to learn if NodeOPCUA might be the right OPC UA stack for your next project.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Previous Experiences<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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When we started exploring the OPC UA protocol and its software ecosystem in 2015, NodeOPCUA was the library we used to build our first rudimentary server, which exposed data from a weather sensor in its address space. Of course we didn’t really know much back then but we were pretty impressed by how easily we could get started and quickly expose a few variable nodes using very little code.<\/p>

Since then, our OPC UA journey focused on C\/C++ based libraries like the now mostly abandoned freeopcua<\/a>\u00a0and later open62541<\/a> because they fitted much better into the software architecture of our projects. After several years of learning, launching and maintaining Qt OPC UA<\/a>, making contributions to the open62541 code base, and completing OPC UA based projects for our customers, we decided to have a fresh look at NodeOPCUA based on the experience we gathered over the last years.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Our Evaluation<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tOur main objective was to find out if the NodeOPCUA module’s feature set would be sufficient to use it in one of our customer projects. So first of all, we made a list of the features we usually need:\n
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  • Loading a custom OPC UA model with structured types, ObjectTypes, EventTypes and fixed objects in the Objects folder<\/li>\n \t
  • All aspects of custom structured types (unions, optional fields, array fields, nested structures)<\/li>\n \t
  • Exposing and connecting to endpoints with all current security policies and security modes<\/li>\n \t
  • Attaching callbacks to Method and Variable nodes on the server<\/li>\n \t
  • Instantiating custom object types with selected optional child nodes<\/li>\n \t
  • Populating and triggering custom events on the server<\/li>\n \t
  • Historizing variables on the server<\/li>\n \t
  • Calling methods from the client<\/li>\n \t
  • Resolving browse paths<\/li>\n \t
  • Reading, writing and monitoring variables of custom structured types<\/li>\n \t
  • Reading the raw history of variable nodes<\/li>\n \t
  • EventNotifier<\/i> monitored items with select and where clause<\/li>\n<\/ul>\nThen we modeled a compact OPC UA nodeset containing the types and structures mentioned above to have everything we need for our evaluation in one place. The exported nodeset XML file was then loaded into a new TypeScript based NodeOPCUA server project and after verifying the successful loading of the nodeset using UaExpert, we started implementing the mentioned features we usually require. A client adapted to interact with the custom server was implemented in a separate TypeScript project in order to evaluate the client API.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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    Observations and Remarks<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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    Coming from C\/C++ based OPC UA implementations, we were really impressed by the way NodeOPCUA handles structured types. The\u00a0<\/span>constructExtensionObject()<\/i>\u00a0method reduces building an extension object containing a custom structured type to just passing an object containing a property for each structure field. Just leaving out or including a property takes care of optional fields and nested structured types are deduced and constructed automatically.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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    const ext = await session.constructExtensionObject(coerceNodeId('ns=2;i=3003'), {\n    int64ArrayMember: [ 1, 2 ],\n    nestedStructArrayMember: [\n        {\n            doubleSubtypeMember: 23\n        },\n        {\n            doubleSubtypeMember: 42,\n        }\n    ]\n}) <\/code><\/pre>