Which interface type lets a client application send data to a server over IP?

An Application Programming Interface (API) is a set of defined rules that enable different software applications to communicate with each other. It specifies how software components should interact, allowing a client application to send data requests to a server and receive responses over IP. Northbound and Southbound interfaces are terms used in network management and SDN (Software-Defined Networking) to describe communication directions between different layers or components, not the general mechanism for client-server data exchange. A Representational State Transfer (REST) API is a type of API that adheres to REST architectural constraints, but "API" is the broader, more accurate answer for the general concept of client-server data transfer.