I've looked through similar questions and tried to Google what I'm trying to do, but I haven't found anything concrete.
What I'm trying to do: where I work, we use an HMI/SCADA system that displays tags, machine states, and other standard SCADA functions. Recently, I figured out how to send HTTP requests from the SCADA system and I tested sending tag values and other similar data to an Express server I spun up, where a value is POSTed approximately every second (for monitoring or reporting; think of a temperature gauge reporting temps every second). Even though the system we use is considered "cutting-edge", the user interface is blocky and lacking, especially when compared to modern web applications. I had the idea to send data from the SCADA system to a POST endpoint, which will then be processed by the Node.js / Express application and reported to an internal website. This way, I can use graphs and charts (from D3 or chart.io) and pre-built UI component libraries like Bootstrap or TailwindCSS.
My question: I use the SCADA application to send an HTTP POST request with a data payload. I can verify that the Express server receives the request and I log the message. However, I don't know how to send the POSTed data to the single (for now) HTML page. I have a simple HTML page with a
fetch() but the SCADA system won't necessarily POST at set intervals, so how do I only make changes to the UI when a POST request is made without polling (ie using a
fetch() every so often from the frontend, which would be a bad idea, I think).
Also, if you can foresee other issues with what I'm trying to do, I would greatly appreciate any feedback. This is uncharted territory for our company, so if it works, we will likely build out reports and other user content in this manner, and I'd like to create a solid foundational architecture to support many requests per second without lag, with instant changes to the UI.