如何使用VB.NET从FTP下载目录

Question

我正在尝试将多个目录从 FTP 服务器下载到我的本地机器，

我试过这个，

Const localFile As String = "C:\Documents and Settings\cr\Desktop\T\New Folder\"
Const remoteFile As String = "textbox.Text"
Const host As String = "ftp://ftp.example.com"
Const username As String = "username"
Const password As String = "password"

For i1 = 0 To ListBox1.SelectedItems.Count - 1
    Dim li As New ListViewItem
    li = ListView1.Items.Add(ListBox1.SelectedItems(i1))
    Dim URI1 As String = host + remoteFile & "/" & ListBox1.SelectedItems(i1)
    Dim ftp1 As System.Net.FtpWebRequest = CType(FtpWebRequest.Create(URI1), FtpWebRequest)
    ftp1.Credentials = New System.Net.NetworkCredential(username, password)
    ftp1.KeepAlive = False
    ftp1.UseBinary = True
    ftp1.Method = System.Net.WebRequestMethods.Ftp.DownloadFile
    Using response As System.Net.FtpWebResponse = CType(ftp1.GetResponse, System.Net.FtpWebResponse)
        Using responseStream As IO.Stream = response.GetResponseStream

            Dim length As Integer = response.ContentLength
            Dim bytes(length) As Byte

            'loop to read & write to file
            Using fs As New IO.FileStream(localFile & ListBox1.SelectedItems(i1), IO.FileMode.Create)
                Dim buffer(2047) As Byte
                Dim read As Integer = 1

                Do
                    read = responseStream.Read(buffer, 0, buffer.Length)
                    fs.Write(buffer, 0, read)

                Loop Until read = 0 'see Note(1)
                responseStream.Close()
                fs.Flush()
                fs.Close()
            End Using
            responseStream.Close()
        End Using

        response.Close()
    End Using
    li.BackColor = Color.Aquamarine
Next

但这里的问题是我可以从文件夹下载多个文件，但无法从主目录下载子目录及其内容。

基本上主目录由文件和子目录组成。 那么有没有办法从FTP下载子目录及其内容？

提前致谢。

Answer 1

将我对C# 的回答翻译通过 FTP将所有文件和子目录下载到 VB.NET：

FtpWebRequest对递归文件下载（或任何其他递归操作）没有任何明确的支持。 您必须自己实现递归：

• 列出远程目录
• 迭代条目，下载文件并递归到子目录（再次列出它们等）

一个棘手的部分是从子目录中识别文件。 无法使用FtpWebRequest以可移植的方式做到这一点。 不幸的是， FtpWebRequest不支持MLSD命令，这是在 FTP 协议中检索具有文件属性的目录列表的唯一可移植方式。 另请参阅检查 FTP 服务器上的对象是文件还是目录。

您的选择是：

• 对文件名进行操作，对于文件肯定会失败而对于目录会成功（反之亦然）。 即您可以尝试下载“名称”。 如果成功，它是一个文件，如果失败，它是一个目录。
• 您可能很幸运，在您的特定情况下，您可以通过文件名区分目录中的文件（即所有文件都有扩展名，而子目录没有）
• 您使用长目录列表（ LIST命令 = ListDirectoryDetails方法）并尝试解析特定于服务器的列表。 许多 FTP 服务器使用 *nix 样式的列表，您可以通过条目开头的d标识目录。 但是许多服务器使用不同的格式。 以下示例使用此方法（假设为 *nix 格式）

Sub DownloadFtpDirectory(
        url As String, credentials As NetworkCredential, localPath As String)
    Dim listRequest As FtpWebRequest = WebRequest.Create(url)
    listRequest.Method = WebRequestMethods.Ftp.ListDirectoryDetails
    listRequest.Credentials = credentials

    Dim lines As List(Of String) = New List(Of String)

    Using listResponse As FtpWebResponse = listRequest.GetResponse(),
          listStream As Stream = listResponse.GetResponseStream(),
          listReader As StreamReader = New StreamReader(listStream)
        While Not listReader.EndOfStream
            lines.Add(listReader.ReadLine())
        End While
    End Using

    For Each line As String In lines
        Dim tokens As String() =
            line.Split(New Char() {" "}, 9, StringSplitOptions.RemoveEmptyEntries)
        Dim name As String = tokens(8)
        Dim permissions As String = tokens(0)

        Dim localFilePath As String = Path.Combine(localPath, name)
        Dim fileUrl As String = url + name

        If permissions(0) = "d" Then
            If Not Directory.Exists(localFilePath) Then
                Directory.CreateDirectory(localFilePath)
            End If
            DownloadFtpDirectory(fileUrl + "/", credentials, localFilePath)
        Else
            Dim downloadRequest As FtpWebRequest = WebRequest.Create(fileUrl)
            downloadRequest.Method = WebRequestMethods.Ftp.DownloadFile
            downloadRequest.Credentials = credentials

            Using downloadResponse As FtpWebResponse = downloadRequest.GetResponse(),
                  sourceStream As Stream = downloadResponse.GetResponseStream(),
                  targetStream As Stream = File.Create(localFilePath)
                Dim buffer As Byte() = New Byte(10240 - 1) {}
                Dim read As Integer
                Do
                    read = sourceStream.Read(buffer, 0, buffer.Length)
                    If read > 0 Then
                        targetStream.Write(buffer, 0, read)
                    End If
                Loop While read > 0
            End Using
        End If
    Next
End Sub

使用如下函数：

Dim credentials As NetworkCredential = New NetworkCredential("user", "mypassword")
Dim url As String = "ftp://ftp.example.com/directory/to/download/"
DownloadFtpDirectory(url, credentials, "C:\target\directory")

---

如果您想避免解析特定于服务器的目录列表格式的麻烦，请使用支持MLSD命令和/或解析各种LIST列表格式的第 3 方库； 和递归下载。

例如，使用WinSCP .NET 程序集，您可以通过一次调用Session.GetFiles来下载整个目录：

' Setup session options
Dim SessionOptions As SessionOptions = New SessionOptions
With SessionOptions
    .Protocol = Protocol.Ftp
    .HostName = "ftp.example.com"
    .UserName = "user"
    .Password = "mypassword"
End With

Using session As Session = New Session()
    ' Connect
    session.Open(SessionOptions)

    ' Download files
    session.GetFiles("/directory/to/download/*", "C:\target\directory\*").Check()
End Using

如果服务器支持，WinSCP 在内部使用MLSD命令。 如果没有，它使用LIST命令并支持数十种不同的列表格式。

Session.GetFiles方法默认是递归的。

（我是 WinSCP 的作者）

Answer 2

查看我的 FTP 课程：非常简单。

看看我的 FTP 类，它可能正是您所需要的。

Public Class FTP
        '-------------------------[BroCode]--------------------------
        '----------------------------FTP-----------------------------
        Private _credentials As System.Net.NetworkCredential
        Sub New(ByVal _FTPUser As String, ByVal _FTPPass As String)
            setCredentials(_FTPUser, _FTPPass)
        End Sub
        Public Sub UploadFile(ByVal _FileName As String, ByVal _UploadPath As String)
            Dim _FileInfo As New System.IO.FileInfo(_FileName)
            Dim _FtpWebRequest As System.Net.FtpWebRequest = CType(System.Net.FtpWebRequest.Create(New Uri(_UploadPath)), System.Net.FtpWebRequest)
            _FtpWebRequest.Credentials = _credentials
            _FtpWebRequest.KeepAlive = False
            _FtpWebRequest.Timeout = 20000
            _FtpWebRequest.Method = System.Net.WebRequestMethods.Ftp.UploadFile
            _FtpWebRequest.UseBinary = True
            _FtpWebRequest.ContentLength = _FileInfo.Length
            Dim buffLength As Integer = 2048
            Dim buff(buffLength - 1) As Byte
            Dim _FileStream As System.IO.FileStream = _FileInfo.OpenRead()
            Try
                Dim _Stream As System.IO.Stream = _FtpWebRequest.GetRequestStream()
                Dim contentLen As Integer = _FileStream.Read(buff, 0, buffLength)
                Do While contentLen <> 0
                    _Stream.Write(buff, 0, contentLen)
                    contentLen = _FileStream.Read(buff, 0, buffLength)
                Loop
                _Stream.Close()
                _Stream.Dispose()
                _FileStream.Close()
                _FileStream.Dispose()
            Catch ex As Exception
                MessageBox.Show(ex.Message, "Upload Error: ", MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub
        Public Sub DownloadFile(ByVal _FileName As String, ByVal _ftpDownloadPath As String)
            Try
                Dim _request As System.Net.FtpWebRequest = System.Net.WebRequest.Create(_ftpDownloadPath)
                _request.KeepAlive = False
                _request.Method = System.Net.WebRequestMethods.Ftp.DownloadFile
                _request.Credentials = _credentials
                Dim _response As System.Net.FtpWebResponse = _request.GetResponse()
                Dim responseStream As System.IO.Stream = _response.GetResponseStream()
                Dim fs As New System.IO.FileStream(_FileName, System.IO.FileMode.Create)
                responseStream.CopyTo(fs)
                responseStream.Close()
                _response.Close()
            Catch ex As Exception
                MessageBox.Show(ex.Message, "Download Error: ", MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub
        Public Function GetDirectory(ByVal _ftpPath As String) As List(Of String)
            Dim ret As New List(Of String)
            Try
                Dim _request As System.Net.FtpWebRequest = System.Net.WebRequest.Create(_ftpPath)
                _request.KeepAlive = False
                _request.Method = System.Net.WebRequestMethods.Ftp.ListDirectoryDetails
                _request.Credentials = _credentials
                Dim _response As System.Net.FtpWebResponse = _request.GetResponse()
                Dim responseStream As System.IO.Stream = _response.GetResponseStream()
                Dim _reader As System.IO.StreamReader = New System.IO.StreamReader(responseStream)
                Dim FileData As String = _reader.ReadToEnd
                Dim Lines() As String = FileData.Split(New String() {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)
                For Each l As String In Lines
                    ret.Add(l)
                Next
                _reader.Close()
                _response.Close()
            Catch ex As Exception
                MessageBox.Show(ex.Message, "Directory Fetch Error: ", MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
            Return ret
        End Function

        Private Sub setCredentials(ByVal _FTPUser As String, ByVal _FTPPass As String)
            _credentials = New System.Net.NetworkCredential(_FTPUser, _FTPPass)
        End Sub
    End Class

初始化：

Dim ftp As New FORM.FTP("username", "password")

ftp.UploadFile("c:\file.jpeg", "ftp://domain/file.jpeg")

ftp.DownloadFile("c:\file.jpeg", "ftp://ftp://domain/file.jpeg")

Dim directory As List(Of String) = ftp.GetDirectory("ftp://ftp.domain.net/")
        ListBox1.Items.Clear()
        For Each item As String In directory
            ListBox1.Items.Add(item)
        Next