WinINet API Reference - Web Services - Windows API

WinINet API

The WinINet API provides high-level access to the HTTP and FTP protocols. It is designed for applications that need to retrieve documents from the Internet, such as web browsers.

Overview

WinINet simplifies the process of making requests to Internet servers. It handles many of the complexities associated with network communication, including:

Establishing connections to Internet servers.
Sending and receiving data.
Managing HTTP headers and status codes.
Handling authentication.
Supporting proxy servers.

Key Concepts

Internet Sessions

An Internet session is established using the InternetOpen function. This function initializes the WinINet library and provides a handle to the session.

HINTERNET InternetOpen(
  LPCWSTR   lpszAgent,
  DWORD     dwAccessType,
  LPCWSTR   lpszProxyName,
  LPCWSTR   lpszProxyBypass,
  DWORD     dwFlags
);

Connections

After establishing an Internet session, you can open a connection to a specific Internet server using the InternetConnect function.

HINTERNET InternetConnect(
  HINTERNET hInternet,
  LPCWSTR   lpszServerName,
  INTERNET_PORT nPort,
  LPCWSTR   lpszUsername,
  LPCWSTR   lpszPassword,
  DWORD     dwService,
  DWORD     dwFlags,
  DWORD_PTR dwContext
);

Requests

To retrieve data from a server, you can open a request using the HttpOpenRequest function and then send it using HttpSendRequest.

HINTERNET HttpOpenRequest(
  HINTERNET hConnect,
  LPCWSTR   lpszVerb,
  LPCWSTR   lpszObjectName,
  LPCWSTR   lpszVersion,
  LPCWSTR   lpszReferer,
  LPCWSTR*  lplpszAcceptTypes,
  DWORD     dwFlags,
  DWORD_PTR dwContext
);

BOOL HttpSendRequest(
  HINTERNET hRequest,
  LPCWSTR   lpszHeaders,
  DWORD     dwHeadersLength,
  LPVOID    lpOptional,
  DWORD     dwOptionalLength,
  DWORD     dwFlags,
  DWORD_PTR dwContext
);

Reading Data

Once a request has been sent and the server has responded, you can read the response data using the InternetReadFile function.

BOOL InternetReadFile(
  HINTERNET hFile,
  LPVOID    lpBuffer,
  DWORD     dwNumberOfBytesToRead,
  LPDWORD   lpdwNumberOfBytesRead
);

Error Handling

WinINet functions return specific error codes that can be retrieved using GetLastError. The InternetGetLastResponseInfo function can provide more detailed information about the last HTTP error.

Note: For more complex scenarios involving asynchronous operations or finer control over HTTP, consider using the WinHTTP API.

Functions

Function	Description
`InternetOpen`	Initializes an application's use of the WinINet API.
`InternetConnect`	Establishes a connection to the specified Internet server.
`HttpOpenRequest`	Opens an HTTP request handle.
`HttpSendRequest`	Sends the request to the HTTP server.
`InternetReadFile`	Reads data from the specified Internet handle.
`InternetCloseHandle`	Closes the specified Internet handle.

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