爲實現Http訪問，微軟提供了二套API：WinINet, WinHTTP。
WinHTTP比WinINet更加安全和健壯，可以這麼認爲WinHTTP是WinINet的升級版本。
下面是WinHTTP常規接口調用步驟：
WintpOpen
WinHttpConnect
WinHttpOpenRequest
WinHttpAddRequestHeaders
WinHttpSendRequest
WinHttpReceiveResponse
WinHttpQueryHeaders
WinHttpReadData
WinHttpCloseHandle
int contextLengthId = WINHTTP_QUERY_CONTENT_LENGTH;
int statusCodeId = WINHTTP_QUERY_STATUS_CODE;