(Visual Basic 6.0) SFTP Upload Large File in Parts

See more SFTP Examples

Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim sftp As New ChilkatSFtp

' Set some timeouts, in milliseconds:
sftp.ConnectTimeoutMs = 5000
sftp.IdleTimeoutMs = 10000

' Connect to the SSH server.  
' The standard SSH port = 22
' The hostname may be a hostname or IP address.
Dim hostname As String
hostname = "sftp.example.com"
Dim port As Long
port = 22
Dim success As Long
success = sftp.Connect(hostname,port)
If (success <> 1) Then
    Debug.Print sftp.LastErrorText
    Exit Sub
End If

' Authenticate with the SSH server.  Chilkat SFTP supports
' both password-based authenication as well as public-key
' authentication.  This example uses password authenication.
success = sftp.AuthenticatePw("myLogin","myPassword")
If (success <> 1) Then
    Debug.Print sftp.LastErrorText
    Exit Sub
End If

' After authenticating, the SFTP subsystem must be initialized:
success = sftp.InitializeSftp()
If (success <> 1) Then
    Debug.Print sftp.LastErrorText
    Exit Sub
End If

' Open a remote file for writing on the SSH server.
' If the file already exists, it is overwritten.
' (Specify "createNew" instead of "createTruncate" to
' prevent overwriting existing files.)
Dim handle As String
handle = sftp.OpenFile("big.zip","writeOnly","createTruncate")
If (sftp.LastMethodSuccess <> 1) Then
    Debug.Print sftp.LastErrorText
    Exit Sub
End If

' We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
' to the SFTP server.
Dim localFilePath As String
localFilePath = "qa_data/zips/big.zip"

' Rather than uploading in one shot, we'll read the local file in chunks
' and upload a chunk at a time.
Dim fac As New CkFileAccess

success = fac.OpenForRead(localFilePath)
If (success = 0) Then
    success = sftp.CloseHandle(handle)
    Debug.Print fac.LastErrorText
    Exit Sub
End If

' If we were to split the local file into 128K chunks, how many chunks (blocks) would
' we have, including the last partial block?
Dim blockSize As Long
blockSize = 131072
Dim numBlocks As Long
numBlocks = fac.GetNumBlocks(blockSize)
Debug.Print "Number of blocks = " & numBlocks

Dim bd As New ChilkatBinData
Dim i As Long
i = 0
Do While i < numBlocks
    ' Read the Nth block, which gets appended to the bd.  (which means
    ' we must clear the contents of bd before the next iteration)
    success = fac.ReadBlockBd(i,blockSize,bd)
    If (success = 0) Then
        success = sftp.CloseHandle(handle)
        Debug.Print fac.LastErrorText
        Exit Sub
    End If

    ' Upload this block to the open remote file.
    success = sftp.WriteFileBd(handle,bd)
    If (success = 0) Then
        Debug.Print sftp.LastErrorText
        Exit Sub
    End If

    ' Clear the contents for the next iteration.
    success = bd.Clear()

    i = i + 1
Loop

' Close the local file.
fac.FileClose 

' -----------------------------------------------------------------------------
' This is important.  You must close the handle on the server.
' Otherwise open handles will accumulate on the server until eventually a limit
' is reached and the server will fail on a call to OpenFile.
' -----------------------------------------------------------------------------

' Close the remote file handle on the server.
success = sftp.CloseHandle(handle)
If (success <> 1) Then
    Debug.Print sftp.LastErrorText
    Exit Sub
End If

Debug.Print "Success."