WinHttpQueryOption function (winhttp.h)

Article
05/24/2022

The WinHttpQueryOption function queries an Internet option on the specified handle.

Syntax

WINHTTPAPI BOOL WinHttpQueryOption(
  [in]      HINTERNET hInternet,
  [in]      DWORD     dwOption,
  [out]     LPVOID    lpBuffer,
  [in, out] LPDWORD   lpdwBufferLength
);

Parameters

[in] hInternet

An HINTERNET handle on which to query information. Note that this can be either a Session handle or a Request handle, depending on what option is being queried; see the Option Flags topic to determine which handle is appropriate to use in querying a particular option.

[in] dwOption

An unsigned long integer value that contains the Internet option to query. This can be one of the Option Flags values.

[out] lpBuffer

A pointer to a buffer that receives the option setting. Strings returned by the WinHttpQueryOption function are globally allocated, so the calling application must globally free the string when it finishes using it. Setting this parameter to NULL causes this function to return FALSE. Calling GetLastError then returns ERROR_INSUFFICIENT_BUFFER and lpdwBufferLength contains the number of bytes required to hold the requested information.

[in, out] lpdwBufferLength

A pointer to an unsigned long integer variable that contains the length of lpBuffer, in bytes. When the function returns, the variable receives the length of the data placed into lpBuffer. If GetLastError returns ERROR_INSUFFICIENT_BUFFER, this parameter receives the number of bytes required to hold the requested information.

Return value

Returns TRUE if successful, or FALSE otherwise. To get a specific error message, call GetLastError. Among the error codes returned are the following:

Error Code	Description
ERROR_WINHTTP_INCORRECT_HANDLE_STATE	The requested operation cannot be carried out because the handle supplied is not in the correct state.
ERROR_WINHTTP_INCORRECT_HANDLE_TYPE	The type of handle supplied is incorrect for this operation.
ERROR_WINHTTP_INTERNAL_ERROR	An internal error has occurred.
ERROR_WINHTTP_INVALID_OPTION	An invalid option value was specified.
ERROR_NOT_ENOUGH_MEMORY	Not enough memory was available to complete the requested operation. (Windows error code)

Remarks

Even when WinHTTP is used in asynchronous mode (that is, when WINHTTP_FLAG_ASYNC has been set in WinHttpOpen), this function operates synchronously. The return value indicates success or failure. To get extended error information, call GetLastError.

GetLastError returns the ERROR_INVALID_PARAMETER if an option flag that is invalid for the specified handle type is passed to the dwOption parameter.

Note For Windows XP and Windows 2000, see the Run-Time Requirements section of the WinHttp start page.

Examples

This example demonstrates retrieving the connection time-out value:

    DWORD data;
    DWORD dwSize = sizeof(DWORD);

    // Use WinHttpOpen to obtain an HINTERNET handle.
    HINTERNET hSession = WinHttpOpen(L"A WinHTTP Example Program/1.0", 
                                    WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
                                    WINHTTP_NO_PROXY_NAME, 
                                    WINHTTP_NO_PROXY_BYPASS, 0);
    if (hSession)
    {


        // Use WinHttpQueryOption to retrieve internet options.
        if (WinHttpQueryOption( hSession, 
                                WINHTTP_OPTION_CONNECT_TIMEOUT, 
                                &data, &dwSize))
        {
            printf("Connection timeout: %u ms\n\n",data);
        }
        else
        {
            printf( "Error %u in WinHttpQueryOption.\n", GetLastError());
        }        
        
        // When finished, release the HINTERNET handle.
        WinHttpCloseHandle(hSession);
    }
    else
    {
        printf("Error %u in WinHttpOpen.\n", GetLastError());
    }

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]
Target Platform	Windows
Header	winhttp.h
Library	Winhttp.lib
DLL	Winhttp.dll
Redistributable	WinHTTP 5.0 and Internet Explorer 5.01 or later on Windows XP and Windows 2000.

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