前段时间研究FTP，利用FTPClient在进行FTP文件传输时如果FTP站点不支持PASV模式，而内网对PORT模式也有限制的时候，多次测试未能成功，转换思路，考虑用WIN API。成功地实现了用C#对WININET.DLL的平台调用，下面将里面用到的函数列表如下：
//下面两个是在实现FTP过程中用到的两个数据结构
[StructLayout(LayoutKind.Sequential,CharSet=CharSet.Auto)]
public class WIN32_FIND_DATA
{
public UInt32 dwFileAttributes=0;
public FILETIME ftCreationTme;
public FILETIME ftLastAccessTime;
public FILETIME ftLastWriteTime;
public UInt32 nFileSizeHigh=0;
public UInt32 nFileSizeLow=0;
public UInt32 dwReserved0=0;
public UInt32 dwReserved1=0;
[MarshalAs( UnmanagedType.ByValTStr, SizeConst=256)] public string cFileName=null;
[MarshalAs( UnmanagedType.ByValTStr, SizeConst=14)] public string cAlternateFileName=null;
};
[StructLayout(LayoutKind.Sequential,CharSet=CharSet.Auto)]
public class FILETIME
{
public int dwLowDateTime=0;
public int dwHighDateTime=0;
};
//以下是对WININET.DLL中的重要函数的托管转换
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool InternetGetLastResponseInfo(ref uint ulError,
[MarshalAs(UnmanagedType.LPTStr)] string strBuffer, ref uint ulBufferLength);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern IntPtr InternetOpen(string strAppName, ulong
ulAccessType, string strProxy, string strProxyBypass, ulong ulFlags);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool InternetFindNextFile(IntPtr hFind,[In,Out] WIN32_FIND_DATA
dirData);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern IntPtr InternetConnect(IntPtr ulSession, string
strServer, uint ulPort, string strUser, string strPassword, uint ulService, uint ulFlags,
uint ulContext);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool InternetGetConnectedState(ref uint ulFlags, uint
ulReserved);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool FtpSetCurrentDirectory(IntPtr ulSession, string
strPath);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern IntPtr FtpFindFirstFile(IntPtr ulSession, string strPath
, [In, Out] WIN32_FIND_DATA dirData, ulong ulFlags, ulong ulContext);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool FtpGetFile(IntPtr ulSession, string strRemoteFile,
string strLocalFile, bool bolFailIfExist, ulong ulFlags, ulong ulInetFals, ulong
ulContext);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool FtpPutFile(IntPtr ulSession, string strLocalFile,
string strRemoteFile, ulong ulFlags, ulong ulContext);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool FtpDeleteFile(IntPtr ulSession, string strFileName);
[DllImport("wininet.dll", CharSet = CharSet.Auto)]
public static extern bool InternetCloseHandle(IntPtr ulSession);
在WININET.DLL中还有很多其他功能的函数，详细内容请看：
翻译了上面的函数，其实已经成功了80%，后面的工作是SO EASY，就是简单地调用，例子我后面抽时间补上，这种方式的好处是只要SERVER端开放了21端口，它就可以穿越防火墙，还是很令人激动的；不过缺点也是有的，无法实现断点续传。从MSDN的介绍上来看，WINDOWS中实现FTP的方式实际上是利用了HTTP协议，而非真正地遵循FTP协议来实现的。
