FtpGetFile函数下载不到最新文件Solution

Posted 2022-12-07 Will.Guo

因cache缓冲问题，之前最近时间下载过，远端文件修改后在下载下载不到最新文件，在FLAG中加入属性INTERNET_FLAG_RELOAD（强制从远端下载）即可，具体如下：

MSDN原文  相关部分已加红

FtpGetFile Function

---

Retrieves a file from the FTP server and stores it under the specified file name, creating a new local file in the process.

Syntax

BOOL FtpGetFile(
    HINTERNET hConnect,
    LPCTSTR lpszRemoteFile,
    LPCTSTR lpszNewFile,
    BOOL fFailIfExists,
    DWORD dwFlagsAndAttributes,
    DWORD dwFlags,
    DWORD_PTR dwContext
);

Parameters

hConnect

[in] Valid handle to an FTP session.

lpszRemoteFile

[in] Pointer to a null-terminated string that contains the name of the file to retrieve from the remote system.

lpszNewFile

[in] Pointer to a null-terminated string that contains the name of the file to create on the local system.

fFailIfExists

[in]  BOOL that indicates whether the function should proceed if a local file of the specified name already exists. If fFailIfExists is TRUE and the local file exists, FtpGetFile fails.

dwFlagsAndAttributes

[in] Unsigned long integer value that contains the file attributes for the new file. This can be any combination of the FILE_ATTRIBUTE_* flags used by the CreateFile  function. For more information on FILE_ATTRIBUTE_* attributes, see CreateFile in the Platform SDK.

dwFlags

[in] Unsigned long integer value that contains the flags that control how the function will handle the file download. The first set of flag values indicates the conditions under which the transfer occurs. These transfer type flags can be used in combination with the second set of flags that control caching.

The application can select one of these transfer type values:

FTP_TRANSFER_TYPE_ASCII

Transfers the file using FTP's ASCII (Type A) transfer method. Control and formatting information is converted to local equivalents.

FTP_TRANSFER_TYPE_BINARY

Transfers the file using FTP's Image (Type I) transfer method. The file is transferred exactly as it exists with no changes. This is the default transfer method.

FTP_TRANSFER_TYPE_UNKNOWN

Defaults to FTP_TRANSFER_TYPE_BINARY.

INTERNET_FLAG_TRANSFER_ASCII

Transfers the file as ASCII.

INTERNET_FLAG_TRANSFER_BINARY

Transfers the file as binary.

The following flags determine how the caching of this file will be done. Any combination of the following flags can be used with the transfer type flag. The possible values are:

INTERNET_FLAG_HYPERLINK

Forces a reload if there was no Expires time and no LastModified time returned from the server when determining whether to reload the item from the network.

INTERNET_FLAG_NEED_FILE

Causes a temporary file to be created if the file cannot be cached.

INTERNET_FLAG_RELOAD

Forces a download of the requested file, object, or directory listing from the origin server, not from the cache.

INTERNET_FLAG_RESYNCHRONIZE

Reloads HTTP resources if the resource has been modified since the last time it was downloaded. All FTP and Gopher resources are reloaded.

dwContext

[in] Pointer to an unsigned long integer value that contains the application-defined value that associates this search with any application data. This is used only if the application has already called InternetSetStatusCallback to set up a status callback function.

Return Value

Returns TRUE if successful, or FALSE otherwise. To get a specific error message, call GetLastError  .

Remarks

FtpGetFile is a high-level routine that handles all the bookkeeping and overhead associated with reading a file from an FTP server and storing it locally. An application that needs to retrieve file data only or that requires close control over the file transfer should use the FtpOpenFile and InternetReadFile functions.

If the dwFlags parameter specifies FILE_TRANSFER_TYPE_ASCII, translation of the file data converts control and formatting characters to local equivalents. The default transfer is binary mode, where the file is downloaded in the same format as it is stored on the server.

Both lpszRemoteFile and lpszNewFile can be either partially or fully qualified file names relative to the current directory.

Function Information

Stock Implementation	wininet.dll
Custom Implementation	No
Header	Wininet.h
Import library	Wininet.lib
Minimum availability	Internet Explorer 3.0
Minimum operating systems	Windows NT 4.0, Windows 95, Windows CE 2.12