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我试图确认这里描述的功能：

http://msdn.microsoft.com/en-us/library/aa384066(VS.85).aspx

WINHTTP_OPTION_CONNECT_RETRIES 设置或检索一个无符号长整数值，该值包含 WinHTTP 尝试连接到主机的次数。Microsoft Windows HTTP 服务 (WinHTTP) 每个 Internet 协议 (IP) 地址仅尝试一次。例如，如果您尝试连接到具有 10 个 IP 地址且 WINHTTP_OPTION_CONNECT_RETRIES 设置为 7 的多宿主主机，则 WinHTTP 仅尝试连接到前七个 IP 地址。给定同一组 10 个 IP 地址，如果 WINHTTP_OPTION_CONNECT_RETRIES 设置为 20，WinHTTP 只尝试这 10 个 IP 地址中的每一个。如果在指定的尝试次数后连接尝试仍然失败，或者在此之前连接超时过期，则取消请求。WINHTTP_OPTION_CONNECT_RETRIES 的默认值为五次尝试。

确实有效。

我的代码是：

int main()
{   
  DWORD dwDownloaded = 0;
  LPSTR pszOutBuffer;
  BOOL  bResults = FALSE;
  HINTERNET  hSession = NULL, 
             hConnect = NULL,
             hRequest = NULL;

  // Use WinHttpOpen to obtain a session handle.
  hSession = WinHttpOpen( L"WinHTTP Example/1.0",  
                          WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
                          WINHTTP_NO_PROXY_NAME, 
                          WINHTTP_NO_PROXY_BYPASS, 0 );
    DWORD data;
    DWORD dwSize = sizeof(DWORD);
    if (hSession)
    {


        // Use WinHttpQueryOption to retrieve internet options.
        if (WinHttpQueryOption( hSession, 
                                WINHTTP_OPTION_CONNECT_RETRIES, 
                                &data, &dwSize))
        {
            printf("Connection Retries: %u \n\n",data);
        }
        else
        {
            printf( "Error %u in WinHttpQueryOption.\n", GetLastError());
        }        
    }
    else
    {
        printf("Error %u in WinHttpOpen.\n", GetLastError());
    }

dwSize = 0;

   // Specify an HTTP server.
  if( hSession )
    hConnect = WinHttpConnect( hSession, L"google.com",
                               INTERNET_DEFAULT_HTTP_PORT, 0 );

  // Create an HTTP request handle.
  if( hConnect )
    hRequest = WinHttpOpenRequest( hConnect, L"GET", NULL,
                                   NULL, WINHTTP_NO_REFERER, 
                                   NULL, 
                                   NULL );

  // Send a request.
  if( hRequest )
    bResults = WinHttpSendRequest( hRequest,
                                   WINHTTP_NO_ADDITIONAL_HEADERS, 0,
                                   WINHTTP_NO_REQUEST_DATA, 0, 
                                   0, 0 );


  // End the request.
  if( bResults )
    bResults = WinHttpReceiveResponse( hRequest, NULL );

  // Keep checking for data until there is nothing left.
  if( bResults )
  {
    do 
    {
      // Check for available data.
      dwSize = 0;
      if( !WinHttpQueryDataAvailable( hRequest, &dwSize ) )
        printf( "Error %u in WinHttpQueryDataAvailable.\n",
                GetLastError( ) );

      // Allocate space for the buffer.
      pszOutBuffer = new char[dwSize+1];
      if( !pszOutBuffer )
      {
        printf( "Out of memory\n" );
        dwSize=0;
      }
      else
      {
        // Read the data.
        ZeroMemory( pszOutBuffer, dwSize+1 );

        if( !WinHttpReadData( hRequest, (LPVOID)pszOutBuffer, 
                              dwSize, &dwDownloaded ) )
          printf( "Error %u in WinHttpReadData.\n", GetLastError( ) );
        else
          printf( "%s", pszOutBuffer );

        // Free the memory allocated to the buffer.
        delete [] pszOutBuffer;
      }
    } while( dwSize > 0 );
  }


  // Report any errors.
  if( !bResults )
    printf( "Error %d has occurred.\n", GetLastError( ) );

  // Close any open handles.
  if( hRequest ) WinHttpCloseHandle( hRequest );
  if( hConnect ) WinHttpCloseHandle( hConnect );
  if( hSession ) WinHttpCloseHandle( hSession );

    getchar();

 return 0;
}

一种测试方法是将其放在您的 C:\WINDOWS\system32\drivers\etc\hosts 文件中：

123.123.123.123 google.com

66.102.7.99 google.com

类型

ping google.com

（这应该失败）然后

ipconfig /displaydns

您应该会看到 google.com 的两条 dns 记录。

如上所述，默认值为 5，这意味着它应该继续尝试第二个 ip，但事实并非如此。我错过了什么？

4

0 回答 0