VB.NET中使用FTP下載檔案的兩種方法

.net沒有專門處理FTP的類，我們可以通過調用系統自帶的FTP.EXE 或者是調用win32 API中的wininet.dll來完成基本操作。希望以下的代碼能為大家抛磚引玉。

方法一： 使用Ftp.exe ，通過process類來調用它。

Imports System.Diagnostics

...

Public Sub GetFileByCallFtp()

'定義ProcessStartInfo，Process的啟動資訊。

Dim psi As New ProcessStartInfo

'ftp.exe的路徑最好放到設定檔裡。

psi.FileName = "C:\WINNT\system32\ftp.exe"

psi.RedirectStandardInput = False

psi.RedirectStandardOutput = True

'該值指示不使用作業系統Shell程式啟動進程。

psi.UseShellExecute = False

'命令集檔案名.注意,路徑中不能有空格.

Dim fileName As String = "C\ftp.txt"

'-s:FileName表示,從檔中讀取控制命令

psi.Arguments = "-s:" + fileName

Dim proc As Process

proc = Process.Start(psi)

'等待進程完成任務

proc.WaitForExit()

'在主控台輸出結果

Console.WriteLine(proc.StandardOutput)

Console.ReadLine()

End Sub

==============================================================================

ftp.txt 裡的內容

方法二，使用win32 api —— wininet.dll

首先是，api聲明：

因為此測試程式，是VB.NET ConsoleApplication所以，api聲明寫在Module裡，

方法是靜態的。所以沒加Shared關鍵字， 這一點請大家注意。

_
Public Function InternetOpen(ByVal sAgent As String, ByVal LAccessType As Integer, ByVal sProxyName As String, _
ByVal SProxyBypass As String, ByVal lFlags As Integer) As Integer
End Function

_
Public Function InternetConnect(ByVal hInternetSession As Integer, ByVal sServerName As String, _
ByVal nServerPort As Integer, ByVal sUsername As String, _
ByVal sPassword As String, ByVal lService As Integer, _
ByVal lFlags As Integer, ByVal lCoNtext As Integer) As Integer
End Function

_
Public Function FtpGetFile(ByVal hFtpSession As Integer, ByVal lpszRemoteFile As String, _
ByVal lpszNewFile As String, ByVal fFailIfExists As Boolean, _
ByVal dwFlagsAndAttributes As Integer, ByVal dwFlags As Integer, _
ByVal dwCoNtext As Integer) As Boolean
End Function

_
Public Function InternetCloseHandle(ByVal hInet As Integer) As Integer
End Function

調用：

Public Sub GetFileByCallWininetDLL()
Try
Dim intinet As Integer = InternetOpen(Nothing, 0, Nothing, Nothing, 0)
If intinet > 0 Then

'參數：intinet的session值，ftp位址，埠，使用者名，密碼，lService， lFlags，lCoNtext

Dim intinetconn As Integer = InternetConnect(intinet, "192.168.110.152", 0, "tokiwa", "tokiwa", 1, 0, 0)

If intinetconn > 0 Then

'下載某個檔到指定檔

Dim ret As Boolean = FtpGetFile(intinetconn, "pagerror.gif", "C:\itest.gif", 0, 0, 1, 0)

If ret Then
Console.WriteLine("ok!")
Console.ReadLine()
End If
InternetCloseHandle(intinetconn)
InternetCloseHandle(intinet)
Else
Console.WriteLine("can't connect!")
Console.ReadLine()
End If

Else
Console.WriteLine("ftp wrong!")
Console.ReadLine()
End If
Catch ex As Exception
Console.WriteLine(ex.Message)
Console.ReadLine()
End Try

End Sub