Read file from FTP

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5.00/5 (2 votes)

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Hello, I am trying to read text from a text file located on an FTP server using VB. I have managed to figure out how to download the file and then read the data, but this is less than ideal. I would like to stream the text into a string where I can manipulate it and move on without ever having to download the file. I am moving very little data...maybe 30kb at most. Any help is appreciated. Thanks

Posted 10-Jun-10 16:28pm

blackbanjo

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2 solutions

Solution 1

Have you tried using a WebBrowser control and navigating to that file?

Say, ftp://ftp.test.com/test.txt

Then

VB

WebBrowser1.Navigate("ftp://ftp.test.com/test.txt")
Dim txtStr as String = WebBrowser1.DocumentText

txtStr will have the source of the page you have navigated to - which ultimately is the content of test.txt

Posted 10-Jun-10 19:22pm

Anshul R

Comments

blackbanjo 11-Jun-10 1:39am

I tried that, but i end up getting the page source, not just the text.

I also need to use a login and password, and this method provides no good way to rectify that.

Anshul R 11-Jun-10 1:45am

For that, there will be a password box.

Use SendKeys.SendWait(Make sure your application is active that time)

First send the Username(as a string)
Then send "{TAB}" - For going to the password box
Then send the password(as a string)
Then send "{TAB}" - For focusing on the OK button.
Then send "{Return}" - equivalent of clicking OK button

blackbanjo 11-Jun-10 1:55am

That may work, but it's not the approach I want to take. I was hoping I could use FTP and read the data into a string. There must be a way to do this.

Anshul R 11-Jun-10 1:56am

To my knowledge, .NET Framework does not have this capability. You might have to write your own FTP Client.

There are good FTP projects in CodeProject

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0x3c0 · Accepted Answer · 2010-06-10T20:35:00

Solution 2

As you've probably worked out, you need to use FTP. The .net framework has some methods which will help you here, in particular System.Net.FtpWebRequest. The general sequence of events that you need to do is:

Create an FtpWebRequest that contains the URL of your file. It would appear that you need to prefix it with ftp://

If you want to use a username and password, set the Credentials property to a NetworkCredential instance

Set the UseBinary property of the FtpWebRequest to true, so that any binary files don't get treated as text

Set the Method property of the FtpWebRequest to WebRequestMethods.Ftp.DownloadFile

From here, you can either go synchronously or asynchronously. The latter option is more complex, but will not hold up your code while it runs. Synchronous is simpler, but will be slower for large files. The general sequence of events is:

Use GetResponse or BeginGetResponse/EndGetResponse to get the FtpWebResponse object

Get the response stream from the FtpWebResponse object

Copy data from the response stream to the stream representing the file, or use a StreamReader instance if you just want to directly read it

Posted 10-Jun-10 20:35pm

0x3c0

Updated 11-Jun-10 1:58am

Chris Maunder772.8K

v4

Comments

blackbanjo 11-Jun-10 16:49pm

Well, I am 100% self-taught so I see where you're going, but I can't quite grasp the concept fully. What I have is this:

Dim URI As String = host & remoteDirectory & filename
Dim ftp As System.Net.FtpWebRequest = CType(System.Net.FtpWebRequest.Create(URI), System.Net.FtpWebRequest)

ftp.Credentials = New System.Net.NetworkCredential(FTPusername, FTPpassword)

ftp.KeepAlive = False

ftp.UseBinary = True

ftp.Method = System.Net.WebRequestMethods.Ftp.DownloadFile

Using response As System.Net.FtpWebResponse = CType(ftp.GetResponse, System.Net.FtpWebResponse)
Using responseStream As IO.Stream = response.GetResponseStream

Using fs As New IO.FileStream(localFile, IO.FileMode.Create)
Dim buffer(2047) As Byte
Dim read As Integer = 0
Do
read = responseStream.Read(buffer, 0, buffer.Length)
fs.Write(buffer, 0, read)
Loop Until read = 0
responseStream.Close()
fs.Flush()
fs.Close()
End Using
responseStream.Close()
End Using
response.Close()
End Using
MsgBox("finished")
End Sub

This downloads the file, but like I mentioned earlier I am trying to avoid this. Am I on the right path? Where next? I know I am missing a super obvious step but I just can't find it.

0x3c0 11-Jun-10 17:07pm

Yes, you're pretty much there. You've got the response stream, now you just need to (I assume you still want to manipulate text) create a System.IO.StreamReader, passing responseStream to the constructor. Then, you can use ReadLine and the associated methods just like you would a normal file

blackbanjo 11-Jun-10 18:58pm

Thanks, I got it working. I get an error, but oddly enough it really doesn't impede anything and all the data streams just fine. This is what I came up with:

Using response As System.Net.FtpWebResponse = CType(ftp.GetResponse, System.Net.FtpWebResponse)
Using responseStream As IO.Stream = response.GetResponseStream
'loop to read & write to file
' Try

Dim sr As New System.IO.StreamReader(responseStream)
Try

Do
line = sr.ReadLine()
strCreds = strCreds & line
Loop Until line Is Nothing
sr.Close()
Catch ex As Exception
'dont do anything, dont know how to fix this error
'just catch the error and move on
End Try

responseStream.Close()

End Using

response.Close()

End Using

Again, thanks so much.

0x3c0 12-Jun-10 4:44am

You're welcome. I suspect that the error comes from the last concatenation of the line variable. At that point, line is Nothing, so it may simply be that you get a NullReferenceException. There are also a few pieces of redundant code - when you close the StreamReader, the underlying Stream is also closed. Beyond that, the stream is closed when it gets Dispose called, as your Using block will do. It won't cause any massive errors, but it's a little inefficient.

A slightly better loop, and one which is less likely to cause an error is:
line = sr.ReadLine()
Do While line IsNot Nothing
strCreds = strCreds & line ' If you wanted better performance and more efficient memory usage, you could use a StringBuilder's Append method
line = sr.ReadLine()
Loop

Donnavan 26-Jul-10 19:02pm

0x3c0 is right about the loop
Another way this could be done without errors is by changing the loop as follows:

While Not sr.EndOfStream
line = sr.ReadLine()
End While

*Thanks I've been looking for how to accomplish the same task for some time now

Donnavan 26-Jul-10 19:03pm

Reason for my vote of 4
Clear and helpful answer