IWinHttpRequest::Open method

Artikkel
01/07/2021

The Open method opens an HTTP connection to an HTTP resource.

Syntax

HRESULT Open(
  [in]           BSTR    Method,
  [in]           BSTR    Url,
  [in, optional] VARIANT Async
);

Parameters

Method [in]

Specifies the HTTP verb used for the Open method, such as "GET" or "PUT". Always use uppercase as some servers ignore lowercase HTTP verbs.

Url [in]

Specifies the name of the resource. This must be an absolute URL.

Async [in, optional]

Indicates whether to open in asynchronous mode.

Value	Meaning
VARIANT_FALSE	Opens the HTTP connection in synchronous mode. A call to Send does not return until WinHTTP has completely received the response.
VARIANT_TRUE	Opens the HTTP connection in asynchronous mode.

Return value

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

Remarks

This method opens a connection to the resource identified in Url using the HTTP verb given in Method.

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, send an HTTP request, and read the response text.

#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))
    {
        // Send Request.
        hr = pIWinHttpRequest->Send(varEmpty);
    }
    if (SUCCEEDED(hr))
    {
        // Get Response text.
        hr = pIWinHttpRequest->get_ResponseText(&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, send an HTTP request, and read the response text.

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

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

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

// Display the response text.
WScript.Echo( WinHttpReq.ResponseText);

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

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