This is what I have read[ here][1] that webhooks needs api.
Is webhooks only specifically meant to publish data to other 3rd party servers such as ubidots & thingspeak?
I cannot find any example of webhooks to link to private localhost server. My apology.
According to this quote, webhooks seem not ideal for my purpose.
[1]: Put data to my own database - #4 by johnyrobot5