Network Application Programming Interfaces (APIs)

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An Application Programming Interface (API) lets computer programmers access the functionality of published software modules and services. An API defines data structures and subroutine calls that can be used to extend existing applications with new features, and build entirely new applications on top of other software components. Some of these APIs specifically support network programming.

Network programming is a type of software development for applications that connect and communicate over computer networks including the Internet. Network APIs provide entry points to protocols and re-usable software libraries. Network APIs support Web browsers, Web databases, and many mobile apps. They are widely supported across many different programming languages and operating systems.

Socket Programming

Traditional network programming followed a client-server model. The primary APIs used for client-server networking were implemented in socket libraries built into operating systems. Berkeley sockets and Windows Sockets (Winsock) APIs were the two primary standards for socket programming for many years.

Remote Procedure Calls 

RPC APIs extend basic network programming techniques by adding the capability for applications to invoke functions on remote devices instead of just sending messages to them. With the explosion of growth on the World Wide Web (WWW), XML-RPC emerged as one popular mechanism for RPC.

Simple Object Access Protocol (SOAP)

SOAP was developed in the late 1990s as a network protocol using XML as its message format and HyperText Transfer Protocol (HTTP) as its transport. SOAP generated a loyal following of Web services programmers and became widely used for enterprise applications.

Representational State Transfer (REST)

REST is another programming model that also supports Web services that arrived on the scene more recently. Like SOAP, REST APIs use HTTP, but instead of XML, REST applications often choose to use a Javascript Object Notation (JSON) instead. REST and SOAP differ greatly in their approaches to state management and security, both key considerations for network programmers. Mobile apps may or may not utilize network APIs, but ones that do often use REST.

The Future of APIs

Both SOAP and REST continue to be actively used for development of new Web services. Being a much newer technology than SOAP, REST is more likely to evolve and produce other offshoots of API development.

Operating systems have also evolved to support the many new Network API technologies. In modern operating systems like Windows 10, for example, sockets continue to be a core API, with HTTP and other additional support layered on top for RESTful style network programming.

As is often the case in computer fields, newer technologies tend to roll out much faster than old ones become obsolete. Look for interesting new API developments to happen especially in the areas of cloud computing and Internet of Things (IoT), where the characteristics of devices and their usage models is quite different from traditional network programming environments.