I am trying to convert some HTTP request code from using the WinHttp COM interface to using lower-level WinInet calls from <wininet.h>
. The COM version is working but I am having difficulty translating the calls into the WinInet API.
This code works fine and gets the correct error response (as the request data is empty) to the POST request:
#import <winhttpcom.dll>
#include <iostream>
#include <string>
int main()
{
HRESULT hr = CoInitialize(NULL);
using namespace WinHttp;
IWinHttpRequestPtr pReq = NULL;
hr = pReq.CreateInstance(__uuidof(WinHttpRequest));
const char* pszReq = "";
if (SUCCEEDED(hr))
{
_bstr_t bstrMethod("POST");
_bstr_t bstrUrl("https://lite.realtime.nationalrail.co.uk/OpenLDBWS/ldb9.asmx");
hr = pReq->Open(bstrMethod, bstrUrl);
pReq->SetRequestHeader(_bstr_t("Content-Type"), _bstr_t("text/*"));
_variant_t vReq(pszReq);
hr = pReq->Send(vReq);
if (SUCCEEDED(hr))
{
_bstr_t bstrResp;
hr = pReq->get_ResponseText(&bstrResp.GetBSTR());
if (SUCCEEDED(hr))
{
std::cout << std::string(bstrResp) << "\n";
}
}
}
CoUninitialize();
}
Saving the output as html, gives this rendering of the response (which is what I expect, since I haven't provided any request data, which would usually include an access token).
This is the code (amended after comments below, and should be reproducible) that I am using to try and replicate this result using wininet.h and the low-level Win32 calls (I realize I haven't closed the handles).
#include <windows.h>
#include <WinInet.h>
#include <iostream>
int main()
{
const char* pszReq = "";
const char* pszUrl = "https://lite.realtime.nationalrail.co.uk/OpenLDBWS/ldb9.asmx";
char szHostName[256];
char szPath[256];
URL_COMPONENTSA comps = {};
comps.dwStructSize = sizeof(comps);
comps.lpszHostName = szHostName;
comps.dwHostNameLength = sizeof(szHostName);
comps.lpszUrlPath = szPath;
comps.dwUrlPathLength = sizeof(szPath);
if (!InternetCrackUrlA(pszUrl, strlen(pszUrl), 0, &comps)) return 1;
HINTERNET hOpen = InternetOpenA("XYZ",INTERNET_OPEN_TYPE_DIRECT,NULL,NULL,0);
if (!hOpen) return 1;
HINTERNET hConnect = InternetConnectA(hOpen,szHostName,comps.nPort,
NULL,NULL,INTERNET_SERVICE_HTTP,0,NULL);
if (!hConnect) return 1;
const char * rgpszAcceptTypes[] = { "text/*", NULL };
HINTERNET hOpenReq = HttpOpenRequestA(hConnect,"POST",szPath,NULL, NULL,
rgpszAcceptTypes, 0,NULL);
if (!hOpenReq) return 1;
const char* pszHeader = "Content-Type: text/xml;charset=UTF-8";
//*** This line returns FALSE ***
BOOL bRet = HttpSendRequestA(hOpenReq, pszHeader, strlen(pszHeader), (LPVOID)pszReq, strlen(pszReq));
//*** LastError is ERROR_HTTP_INVALID_SERVER_RESPONSE
DWORD dwErr = GetLastError();
return 0;
}
All the WinInet handles are non-zero, suggesting the calls are working, but the last HttpSendRequestA()
is returning FALSE immediately, with LastError set to ERROR_HTTP_INVALID_SERVER_RESPONSE.
Clearly the COM route hides a lot of intermediate working, and presumably some constants are defaulted to specific values. It may also be adding other header information, I suppose.
Perhaps someone can suggest where I am going wrong?
CodePudding user response:
There are some mistakes in your WinInet code:
the
pszServerName
value needs to be just the host name by itself, not a full URL. If you have a URL as input, you can parse it into its constituent pieces usingInternetCrackUrlA()
.the 3rd parameter of
HttpOpenRequestA()
is the requested resource relative topszServerName
. So, in your example, you need to use"/"
to request the root resource.the 1st parameter of
HttpSendRequestA()
needs to behOpenReq
, nothOpen
. Also, you should not be including the null-terminators in your buffer sizes.
If you have not already done so, you should have a look at WinInet's documentation on HTTP Sessions.
With that said, try this:
#include <windows.h>
#include <WinInet.h>
#include <iostream>
const char * pszUrl = "https://someUrl";
const char * pszReq = "A string of request data";
const char* pszHeader = "Content-Type: text/xml;charset=UTF-8";
char szHostName[256];
char szPath[256];
URL_COMPONENTSA comps = {};
comps.dwStructSize = sizeof(comps);
comps.lpszHostName = szHostName;
comps.dwHostNameLength = sizeof(szHostName);
comps.lpszUrlPath = szPath;
comps.dwUrlPathLength = sizeof(szPath);
BOOL bRet = InternetCrackUrlA(pszUrl, strlen(pszUrl), 0, &comps);
if (!bRet) ...
HINTERNET hOpen = InternetOpenA("XYZ", INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0);
if (!hOpen) ...
HINTERNET hConnect = InternetConnectA(hOpen, szHostName, comps.nPort, NULL, NULL, INTERNET_SERVICE_HTTP, 0, NULL);
if (!hConnect) ...
HINTERNET hOpenReq = HttpOpenRequestA(hConnect, "POST", szPath, NULL, NULL, NULL, comps.nScheme == INTERNET_SCHEME_HTTPS ? INTERNET_FLAG_SECURE : 0, NULL);
if (!hOpenReq) ...
bRet = HttpSendRequestA(hOpenReq, pszHeader, strlen(pszHeader), pszReq, strlen(pszReq));
if (!bRet) ...
...