REST
From DataFlex Wiki
With DataFlex you can create RESTful web services as well as consume those web services.
Client side
Consuming REST services was made a lot easier since DataFlex 19.0 when it added native JSON support.
Consume a REST service: See cJsonHttpTransfer and JSON Parsing and Transfer
Server side
Creating REST web services has been made easy since DataFlex 19.1 with the introduction of the cWebHttpHandler handler.
You can create a REST service with earlier DataFlex versions, see here for how-to do so in DataFlex 19.0, but it is probably better to use DataFlex 19.1 in that case.
External references
http://salzlechner.com/dev/2016/03/02/interfacing-dataflex-restful-web-services/