Wininet HTTP Client Example

http_client_get.cc

#include <windows.h>
#include <wininet.h>
#include <stdio.h>

#pragma comment (lib, "Wininet.lib")

int main(int argc, char *argv[]) {

	HINTERNET hSession = InternetOpen(
		L"Mozilla/5.0", // User-Agent
		INTERNET_OPEN_TYPE_PRECONFIG,
		NULL,
		NULL,
		0);

	HINTERNET hConnect = InternetConnect(
		hSession,
		L"www.google.com", // HOST
		0,
		L"",
		L"",
		INTERNET_SERVICE_HTTP,
		0,
		0);

	HINTERNET hHttpFile = HttpOpenRequest(
		hConnect,
		L"GET", // METHOD
		L"/",   // URI
		NULL,
		NULL,
		NULL,
		0,
		0);

	while (!HttpSendRequest(hHttpFile, NULL, 0, 0, 0)) {
		printf("HttpSendRequest error : (%lu)\n", GetLastError());

		InternetErrorDlg(
			GetDesktopWindow(),
			hHttpFile,
			ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED,
			FLAGS_ERROR_UI_FILTER_FOR_ERRORS |
			FLAGS_ERROR_UI_FLAGS_GENERATE_DATA |
			FLAGS_ERROR_UI_FLAGS_CHANGE_OPTIONS,
			NULL);
	}

  /*
	char bufQuery[32];

	DWORD dwLengthBufQuery;
	dwLengthBufQuery = sizeof(bufQuery);

	DWORD dwIndex;
	dwIndex = 0;
	
	// get Content-Length value but... too small
	BOOL bQuery;
	bQuery = HttpQueryInfo(
		hHttpFile,
		HTTP_QUERY_CONTENT_LENGTH,
		bufQuery,
		&dwLengthBufQuery,
		&dwIndex);

	if (!bQuery)
		printf("HttpQueryInfo error : <%lu>\n", GetLastError());
	*/

	DWORD dwFileSize;
	//dwFileSize = (DWORD)atol(bufQuery);
	dwFileSize = BUFSIZ;

	char* buffer;
	buffer = new char[dwFileSize + 1];

	while (true) {
		DWORD dwBytesRead;
		BOOL bRead;

		bRead = InternetReadFile(
			hHttpFile,
			buffer,
			dwFileSize + 1,
			&dwBytesRead);

		if (dwBytesRead == 0) break;

		if (!bRead) {
			printf("InternetReadFile error : <%lu>\n", GetLastError());
		} else {
			buffer[dwBytesRead] = 0;
			printf("Retrieved %lu data bytes: %s\n", dwBytesRead, buffer);
		}
	}

	InternetCloseHandle(hHttpFile);
	InternetCloseHandle(hConnect);
	InternetCloseHandle(hSession);

	return 0;
}

https_client_get.cc

#include <windows.h>
#include <wininet.h>
#include <stdio.h>

#pragma comment (lib, "Wininet.lib")

int main(int argc, char *argv[]) {

	HINTERNET hSession = InternetOpen(
		L"Mozilla/5.0",
		INTERNET_OPEN_TYPE_PRECONFIG,
		NULL,
		NULL,
		0);

	HINTERNET hConnect = InternetConnect(
		hSession,
		L"www.google.com",
		INTERNET_DEFAULT_HTTPS_PORT, // THIS
		L"",
		L"",
		INTERNET_SERVICE_HTTP,
		0,
		0);

	HINTERNET hHttpFile = HttpOpenRequest(
		hConnect,
		L"GET",
		L"/",
		NULL,
		NULL,
		NULL,
		INTERNET_FLAG_SECURE, // THIS
		0);

	while (!HttpSendRequest(hHttpFile, NULL, 0, 0, 0)) {
		printf("HttpSendRequest error : (%lu)\n", GetLastError());

		InternetErrorDlg(
			GetDesktopWindow(),
			hHttpFile,
			ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED,
			FLAGS_ERROR_UI_FILTER_FOR_ERRORS |
			FLAGS_ERROR_UI_FLAGS_GENERATE_DATA |
			FLAGS_ERROR_UI_FLAGS_CHANGE_OPTIONS,
			NULL);
	}

	DWORD dwFileSize;
	dwFileSize = BUFSIZ;

	char* buffer;
	buffer = new char[dwFileSize + 1];

	while (true) {
		DWORD dwBytesRead;
		BOOL bRead;

		bRead = InternetReadFile(
			hHttpFile,
			buffer,
			dwFileSize + 1,
			&dwBytesRead);

		if (dwBytesRead == 0) break;

		if (!bRead) {
			printf("InternetReadFile error : <%lu>\n", GetLastError());
		}
		else {
			buffer[dwBytesRead] = 0;
			printf("Retrieved %lu data bytes: %s\n", dwBytesRead, buffer);
		}
	}

	InternetCloseHandle(hHttpFile);
	InternetCloseHandle(hConnect);
	InternetCloseHandle(hSession);

	return 0;
}

Add custom header: HttpAddRequestHeaders

...
	0);

WCHAR szHeader[BUFSIZ] = { 0 };

lstrcpy(szHeader, L"User-Agent: Mozilla/5.0\r\n");
lstrcat(szHeader, L"\r\n");

HttpAddRequestHeaders(hHttpFile, szHeader, -1, HTTP_ADDREQ_FLAG_ADD);

while (!HttpSendRequest(hHttpFile, NULL, 0, 0, 0)) {
...

https://msdn.microsoft.com/ko-kr/library/windows/desktop/aa384233(v=vs.85).aspx

Wininet API make cache automatically, we must use INTERNET_FLAG_RELOAD flag to prevent fetch page from cache..

Wow! Thanks so much AhnMo for posting this complete yet simple WinINet code that works! With only a couple of slight modifications was able to get this working with my requirements. Thanks again for doing this for the community. Best wishes!

This is nice! Is there a way to pass parameters using these same functions?