What is the smart hub LAN protocol to communicate with smart devices over wifi

For the Smart Things that do not use Z-Wave or Zigbee technology and communicate over wifi, what protocol do they use to exchange data with the smart hub? Is it https TLS/SSL encryption or is it something like CoAP?

Do you have a specific brand / model in mind?

As far as I know, there isn’t a single universal protocol. They likely use something over TCP (or UDP) but that’s as far as we can conclude in general. They might use REST-APIs or …, and common or uncommon security / encryption techniques.