问题
We need to get about 100 very small files from a remote FTP server using vb.net. Our company won't let us buy (or install) any 3rd party ftp libraries... so we are forced to use something like FtpWebRequest. (Or is there a better free, choice that is already a part of Visual Studio?)
This method works, but it is VERY slow. (I assume because of the constant logging in/out.)
Log in with user name and password. Get a file-list from the remote server. Log out Use that file-list to get each file separtely: Log in, get the file, log out. Log in 99 more times, get each file, log out each time.
Instead, we probably should be doing this, but it never works:
Log in with user name and password. ONCE. Get a list of filenames. Download each file. Log out ONCE.
We found COUNTLESS examples online of "getting an FTP file list" and later "how to download 1 file with FTP"... but we never see "get EACH file name, and download it NOW".
Dim fwr As Net.FtpWebRequest = Net.FtpWebRequest.Create(ftpSite)
fwr.Credentials = New NetworkCredential(userName, password)
fwr.KeepAlive = True
fwr.Method = WebRequestMethods.Ftp.ListDirectory
Dim sr As IO.StreamReader = Nothing
Try
sr = New IO.StreamReader(fwr.GetResponse().GetResponseStream())
Do Until (sr.EndOfStream())
fileName = sr.ReadLine()
fwr.Method = WebRequestMethods.Ftp.DownloadFile
output = ""
Dim sr2 As IO.StreamReader = Nothing
Try
sr2 = New IO.StreamReader(fwr.GetResponse().GetResponseStream())
output = sr2.ReadToEnd()
Catch ex As Exception
End Try
If (Not sr2 Is Nothing) Then sr2.Close() : sr2 = Nothing
Call MsgBox("Got " & fileName & LF & output)
Loop
Catch ex As Exception
End Try
If (Not sr Is Nothing) Then sr.Close() : sr = Nothing
If (Not fwr Is Nothing) Then fwr = Nothing
回答1:
Take a look at my FTP class, it might be exactly what you need.
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
To initialize:
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
回答2:
Something I just put together, the important part is the fwr.Proxy = Nothing, otherwise it tries to auto get the proxy settings which causes huge delays so setting it to nothing forces it to not use one.
If you are using a proxy obviously you need to set this to an actual proxy.
Dim fwr As Net.FtpWebRequest = Net.FtpWebRequest.Create(ftpAddress)
fwr.Credentials = New NetworkCredential(userName, password)
fwr.KeepAlive = True
fwr.Method = WebRequestMethods.Ftp.ListDirectory
fwr.Proxy = Nothing
Try
Dim sr As New IO.StreamReader(fwr.GetResponse().GetResponseStream())
Dim lst = sr.ReadToEnd().Split(vbNewLine)
For Each file As String In lst
file = file.Trim() 'remove any whitespace
If file = ".." OrElse file = "." Then Continue For
Dim fwr2 As Net.FtpWebRequest = Net.FtpWebRequest.Create(ftpAddress & file)
fwr2.Credentials = fwr.Credentials
fwr2.KeepAlive = True
fwr2.Method = WebRequestMethods.Ftp.DownloadFile
fwr2.Proxy = Nothing
Dim fileSR As New IO.StreamReader(fwr2.GetResponse().GetResponseStream())
Dim fileData = fileSR.ReadToEnd()
fileSR.Close()
Next
sr.Close()
Catch ex As Exception
End Try
I know its a bit late but hopefully helps
来源：https://stackoverflow.com/questions/5938893/using-ftp-to-download-each-file-while-getting-the-file-list