HTTP Overview

This section provides an overview of the HTTP client and server APIs available in Windows. These APIs allow applications to send and receive HTTP requests and responses, enabling seamless communication over the internet.

Core Concepts

HTTP (Hypertext Transfer Protocol) is the foundation of data communication for the World Wide Web. Understanding its fundamental concepts is crucial for effective network programming:

Requests and Responses: Clients send requests to servers, and servers respond with data or status codes.
Methods: Common HTTP methods include GET, POST, PUT, DELETE, etc., each defining the action to be performed on the resource.
Headers: Metadata about the request or response, such as content type, cache control, and authentication information.
URIs: Uniform Resource Identifiers are used to locate resources on the web.
Status Codes: Indicate the outcome of a request (e.g., 200 OK, 404 Not Found, 500 Internal Server Error).

Windows HTTP APIs

Windows offers a comprehensive set of APIs to interact with HTTP. The primary interfaces are:

WinHTTP: A lower-level API designed for server-side applications and services. It provides greater control and flexibility.
WinINet: A higher-level API suitable for client-side applications like web browsers. It handles many details automatically, such as caching and proxy settings.

WinHTTP

WinHTTP is the recommended API for most server applications and services. It offers:

Support for HTTP, HTTPS, and FTP protocols.
Asynchronous operation for non-blocking network calls.
Detailed control over request headers, body, and response handling.
Session management and connection pooling.

Key functions include WinHttpOpen, WinHttpConnect, WinHttpOpenRequest, WinHttpSendRequest, and WinHttpReadData.

WinINet

WinINet is ideal for client applications. It simplifies common internet tasks and integrates well with the Windows Internet Explorer settings.

Automatic handling of proxy servers and Internet options.
Support for HTTP, HTTPS, and FTP.
Caching capabilities.
Functions like InternetOpen, InternetConnect, HttpOpenRequest, HttpSendRequest, and InternetReadFile.

Choosing the Right API

The choice between WinHTTP and WinINet depends on your application's requirements:

Use WinHTTP for services, background tasks, or when fine-grained control over HTTP communication is needed.
Use WinINet for typical client applications, especially those that need to leverage existing Internet Explorer settings and caching.