IWinHttpRequest::SetRequestHeader method

Article
01/07/2021

The SetRequestHeader method adds, changes, or deletes an HTTP request header.

Syntax

HRESULT SetRequestHeader(
  [in] BSTR Header,
  [in] BSTR Value
);

Parameters

Header [in]: Specifies the name of the header to be set, for example, "depth". This parameter should not contain a colon and must be the actual text of the HTTP header.
Value [in]: Specifies the value of the header, for example, "infinity".

Return value

The return value is S_OK on success or an error value otherwise.

Remarks

Headers are transferred across redirects. This can create a security vulnerability. To avoid having headers transferred if a redirect occurs, use the WINHTTP_STATUS_CALLBACK callback to correct the specific headers when a redirect occurs.

The SetRequestHeader method enables the calling application to add or delete an HTTP request header prior to sending the request. The header name is given in Header, and the header token or value is given in Value. To add a header, supply a header name and value. If another header already exists with this name, it is replaced. To delete a header, set Header to the name of the header to delete and set Value to NULL.

The name and value of request headers added with this method are validated. Headers must be well formed. For more information about valid HTTP headers, see RFC 2616. If an invalid header is used, an error occurs and the header is not added.

Note

For Windows XP and Windows 2000, see the Run-Time Requirements section of the WinHTTP Start Page.

Examples

The following example shows how to open an HTTP connection, set a request header, send an HTTP request, and read the response text. This example must be run from a command prompt.

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

#include "httprequest.h"

#pragma comment(lib, "ole32.lib")
#pragma comment(lib, "oleaut32.lib")

// IID for IWinHttpRequest.
const IID IID_IWinHttpRequest =
{
  0x06f29373,
  0x5c5a,
  0x4b54,
  {0xb0, 0x25, 0x6e, 0xf1, 0xbf, 0x8a, 0xbf, 0x0e}
};

int main()
{
    // Variable for return value
    HRESULT    hr;

    // Initialize COM.
    hr = CoInitialize( NULL );

    IWinHttpRequest *  pIWinHttpRequest = NULL;

    BSTR            bstrResponse = NULL;
    VARIANT         varFalse;
    VARIANT         varEmpty;

    CLSID           clsid;

    VariantInit(&varFalse);
    V_VT(&varFalse)   = VT_BOOL;
    V_BOOL(&varFalse) = VARIANT_FALSE;

    VariantInit(&varEmpty);
    V_VT(&varEmpty) = VT_ERROR;

    hr = CLSIDFromProgID(L"WinHttp.WinHttpRequest.5.1", &clsid);

    if (SUCCEEDED(hr))
    {
        hr = CoCreateInstance(clsid, NULL,
                              CLSCTX_INPROC_SERVER,
                              IID_IWinHttpRequest,
                              (void **)&pIWinHttpRequest);
    }
    if (SUCCEEDED(hr))
    {    // Open WinHttpRequest.
        BSTR bstrMethod  = SysAllocString(L"GET");
        BSTR bstrUrl = SysAllocString(L"https://microsoft.com");
        hr = pIWinHttpRequest->Open(bstrMethod, bstrUrl, varFalse);
        SysFreeString(bstrMethod);
        SysFreeString(bstrUrl);
    }
    if (SUCCEEDED(hr))
    {    // Set request header.
        BSTR bstrName  = SysAllocString(L"Date");
        BSTR bstrValue = SysAllocString(L"Fri, 16 Mar 2001 00:25:54 GMT");
        hr = pIWinHttpRequest->SetRequestHeader(bstrName, bstrValue);
        SysFreeString(bstrName);
        SysFreeString(bstrValue);
    }
    if (SUCCEEDED(hr))
    {    // Send Request.
        hr = pIWinHttpRequest->Send(varEmpty);
    }
    if (SUCCEEDED(hr))
    {    // Get Response headers.
        hr = pIWinHttpRequest->GetAllResponseHeaders(&bstrResponse);
    }
    if (SUCCEEDED(hr))
    {    // Print the response to a console.
        wprintf(L"%.256s",bstrResponse);
    }

    // Release memory.
    if (pIWinHttpRequest)
        pIWinHttpRequest->Release();
    if (bstrResponse)
        SysFreeString(bstrResponse);

    CoUninitialize();
    return 0;
}

The following scripting example shows how to open an HTTP connection, set a request header, and send an HTTP request.

// Instantiate a WinHttpRequest object.
var WinHttpReq = new ActiveXObject("WinHttp.WinHttpRequest.5.1");

// Initialize an HTTP request.  
WinHttpReq.Open("GET", "https://www.microsoft.com", false);

// Add/replace a request header.
WinHttpReq.SetRequestHeader("Date", Date());

// Send the HTTP request.
WinHttpReq.Send();

Requirements

Requirement	Value
Minimum supported client	Windows XP, Windows 2000 Professional with SP3 [desktop apps only]
Minimum supported server	Windows Server 2003, Windows 2000 Server with SP3 [desktop apps only]
Redistributable	WinHTTP 5.0 and Internet Explorer 5.01 or later on Windows XP and Windows 2000.
IDL	HttpRequest.idl
Library	Winhttp.lib
DLL	Winhttp.dll