Send data from C Program to Node-Red

Hi,
I'm newbie to Node-Red.
I work on a Raspberry Pi3.
I developed a C program that runs on the Raspberry. I want to periodically send data to Node-Red.
What is the best way.
Thank you for your comeback.

I would look at using MQTT. I am sure there must be an MQTT library for C.

Lots of ways to do this. I suggest expanding your requirements which might help us give more focused help.

Thank you Colin and Julian.
I am rather electronic.
I made an embedded device and I want to make a graphical interface (web server) to view 2 parameters, every 500 ms. These 2 parameters are the result of a calculation from my C program. The C program and the web server (with Node-RED) runs on the same Raspberry.
I think that eventually I will also use the web server to pass parameter to my embedded device, for its configuration.

For my need, described above:
Are websockets adapted?
Is it better to investigate MQTT or another technology?
Nobody to help me?

You could use web sockets if you are happy to code them on C. Or just a local udp connection. Or tcp. Up to you.

There are many ways it could be done, it is likely to be a case of picking an approach you're most comfortable with.

One option that hasn't been suggested yet is to run your C program using the Node-RED Exec node, and capture whatever it prints to stdout in your node-red flow. We have a number of nodes that use that technique under the covers; they invoke a python script to interface with particular bits of hardware and use stdin/out to communicate with it.