B4X

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. B4X

Dim success As Boolean = False

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

Dim sftp As ChilkatSFtp
sftp.Initialize("sftp")

'  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 = "sftp.example.com"
Dim port As Int = 22
success = sftp.Connect(hostname, port)
If success <> True Then
    Log(sftp.LastErrorText)
    Return
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 <> True Then
    Log(sftp.LastErrorText)
    Return
End If


'  After authenticating, the SFTP subsystem must be initialized:
success = sftp.InitializeSftp
If success <> True Then
    Log(sftp.LastErrorText)
    Return
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 = sftp.OpenFile("big.zip", "writeOnly", "createTruncate")
If sftp.LastMethodSuccess <> True Then
    Log(sftp.LastErrorText)
    Return
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 = "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 ChilkatFileAccess
fac.Initialize

success = fac.OpenForRead(localFilePath)
If success = False Then
    sftp.CloseHandle(handle)
    Log(fac.LastErrorText)
    Return
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 Int = 131072
Dim numBlocks As Int = fac.GetNumBlocks(blockSize)
Log("Number of blocks = " & numBlocks)

Dim bd As ChilkatBinData
bd.Initialize
Dim i As Int = 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 = False Then
        sftp.CloseHandle(handle)
        Log(fac.LastErrorText)
        Return
    End If


    '  Upload this block to the open remote file.
    success = sftp.WriteFileBd(handle, bd)
    If success = False Then
        Log(sftp.LastErrorText)
        Return
    End If


    '  Clear the contents for the next iteration.
    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 <> True Then
    Log(sftp.LastErrorText)
    Return
End If


Log("Success.")