(Lianja) SFTP Upload Large File in Parts

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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 Lianja Extension Download Chilkat Lianja Extension

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

loSftp = createobject("CkSFtp")

// Set some timeouts, in milliseconds:
loSftp.ConnectTimeoutMs = 5000
loSftp.IdleTimeoutMs = 10000

// Connect to the SSH server.  
// The standard SSH port = 22
// The hostname may be a hostname or IP address.
lcHostname = "sftp.example.com"
lnPort = 22
llSuccess = loSftp.Connect(lcHostname,lnPort)
if (llSuccess <> .T.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

// Authenticate with the SSH server.  Chilkat SFTP supports
// both password-based authenication as well as public-key
// authentication.  This example uses password authenication.
llSuccess = loSftp.AuthenticatePw("myLogin","myPassword")
if (llSuccess <> .T.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

// After authenticating, the SFTP subsystem must be initialized:
llSuccess = loSftp.InitializeSftp()
if (llSuccess <> .T.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

// 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.)
lcHandle = loSftp.OpenFile("big.zip","writeOnly","createTruncate")
if (loSftp.LastMethodSuccess <> .T.) then
    ? loSftp.LastErrorText
    release loSftp
    return
endif

// 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.
lcLocalFilePath = "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.
loFac = createobject("CkFileAccess")

llSuccess = loFac.OpenForRead(lcLocalFilePath)
if (llSuccess = .F.) then
    loSftp.CloseHandle(lcHandle)
    ? loFac.LastErrorText
    release loSftp
    release loFac
    return
endif

// If we were to split the local file into 128K chunks, how many chunks (blocks) would
// we have, including the last partial block?
lnBlockSize = 131072
lnNumBlocks = loFac.GetNumBlocks(lnBlockSize)
? "Number of blocks = " + str(lnNumBlocks)

loBd = createobject("CkBinData")
i = 0
do while i < lnNumBlocks
    // Read the Nth block, which gets appended to the bd.  (which means
    // we must clear the contents of bd before the next iteration)
    llSuccess = loFac.ReadBlockBd(i,lnBlockSize,loBd)
    if (llSuccess = .F.) then
        loSftp.CloseHandle(lcHandle)
        ? loFac.LastErrorText
        release loSftp
        release loFac
        release loBd
        return
    endif

    // Upload this block to the open remote file.
    llSuccess = loSftp.WriteFileBd(lcHandle,loBd)
    if (llSuccess = .F.) then
        ? loSftp.LastErrorText
        release loSftp
        release loFac
        release loBd
        return
    endif

    // Clear the contents for the next iteration.
    loBd.Clear()

    i = i + 1
enddo

// Close the local file.
loFac.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.
llSuccess = loSftp.CloseHandle(lcHandle)
if (llSuccess <> .T.) then
    ? loSftp.LastErrorText
    release loSftp
    release loFac
    release loBd
    return
endif

? "Success."


release loSftp
release loFac
release loBd