WinINet API Reference

The WinINet (Windows Internet) API provides high-level functions for interacting with HTTP and FTP protocols. It is primarily intended for client applications requiring Internet functionality.

Contents

Functions
Structures
Constants
Code Samples

Functions

InternetOpen

Initializes an application's use of WinINet functions.

InternetConnect

Creates a connection handle for an HTTP server.

HttpOpenRequest

Creates an HTTP request handle.

HttpSendRequest

Sends the specified request to the HTTP server.

InternetReadFile

Reads data from a handle opened by WinINet.

InternetCloseHandle

Closes an Internet handle.

InternetSetOption

Sets an Internet option on a handle.

InternetGetLastResponseInfo

Retrieves the last response code from an HTTP request.

Structures

typedef struct {
    DWORD   dwFlags;
    DWORD   dwTimeout;
    DWORD   dwRetryInterval;
    DWORD   dwCacheTimeout;
} INTERNET_BUFFERS;

Used to specify buffer information for reading and writing data.

Constants

INTERNET_OPEN_TYPE_PRECONFIG – Use system default proxy settings.
INTERNET_FLAG_RELOAD – Force a fresh request, ignoring the cache.
INTERNET_OPTION_CONNECT_TIMEOUT – Sets the timeout for establishing a connection.

Code Sample – Simple HTTP GET

#include <windows.h>
#include <wininet.h>
#pragma comment(lib, "wininet.lib")

int main() {
    HINTERNET hSession = InternetOpen(L"MyApp",
        INTERNET_OPEN_TYPE_PRECONFIG,
        NULL, NULL, 0);
    if (!hSession) return 1;

    HINTERNET hConnect = InternetConnect(hSession,
        L"example.com", INTERNET_DEFAULT_HTTP_PORT,
        NULL, NULL, INTERNET_SERVICE_HTTP, 0, 0);
    if (!hConnect) { InternetCloseHandle(hSession); return 1; }

    HINTERNET hRequest = HttpOpenRequest(hConnect,
        L"GET", L"/", NULL, NULL, NULL,
        INTERNET_FLAG_RELOAD, 0);
    if (!hRequest) { InternetCloseHandle(hConnect); InternetCloseHandle(hSession); return 1; }

    if (!HttpSendRequest(hRequest, NULL, 0, NULL, 0)) {
        InternetCloseHandle(hRequest);
        InternetCloseHandle(hConnect);
        InternetCloseHandle(hSession);
        return 1;
    }

    char buffer[4096];
    DWORD bytesRead;
    while (InternetReadFile(hRequest, buffer, sizeof(buffer) - 1, &bytesRead) && bytesRead) {
        buffer[bytesRead] = 0;
        printf("%s", buffer);
    }

    InternetCloseHandle(hRequest);
    InternetCloseHandle(hConnect);
    InternetCloseHandle(hSession);
    return 0;
}

This example demonstrates opening a session, connecting to example.com, sending a GET request, and printing the response.