VB.NET

Read Bytes from a Remote SFTP File (BinData)

Demonstrates the Chilkat SFtp.ReadFileBd method, which reads up to a number of bytes from the current position of an open handle and appends them to a BinData. The arguments are the handle, the maximum number of bytes, and the BinData. This example reads in chunks until end-of-file.

Background: For binary files, reading into a BinData preserves the bytes exactly, unlike a text read that decodes through a charset. Because it appends, the chunked read loop accumulates the whole file in the BinData; each pass reads up to the chunk size and the loop repeats until Eof. Fewer bytes than requested can come back near the end of the file, which is normal.

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Dim success As Boolean = False

'  Demonstrates the SFtp.ReadFileBd method, which reads up to a number of bytes from the current
'  position of an open handle and appends them to a BinData.  The 1st argument is the handle, the
'  2nd is the maximum number of bytes, and the 3rd is the BinData.

Dim sftp As New Chilkat.SFtp

'  Connect, authenticate, and initialize the SFTP subsystem.
Dim port As Integer = 22
success = sftp.Connect("sftp.example.com",port)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  Normally you would not hard-code the password in source.  You should instead obtain it
'  from an interactive prompt, environment variable, or a secrets vault.
Dim password As String = "mySshPassword"

success = sftp.AuthenticatePw("mySshLogin",password)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


success = sftp.InitializeSftp()
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


Dim handle As String = sftp.OpenFile("subdir/image.png","readOnly","openExisting")
If (sftp.LastMethodSuccess = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  Read the file in chunks until end-of-file, accumulating the bytes in a BinData.
Dim bd As New Chilkat.BinData
Dim chunkSize As Integer = 8192
Dim reading As Boolean = True
While reading
    success = sftp.ReadFileBd(handle,chunkSize,bd)
    If (sftp.LastReadFailed(handle)) Then
        Debug.WriteLine(sftp.LastErrorText)
        Exit Sub
    End If


    reading = Not sftp.Eof(handle)
End While

success = sftp.CloseHandle(handle)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("Read " & bd.NumBytes & " bytes.")

sftp.Disconnect()