(Delphi ActiveX) 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 for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
sftp: TChilkatSFtp;
hostname: WideString;
port: Integer;
success: Integer;
handle: WideString;
localFilePath: WideString;
fac: TCkFileAccess;
blockSize: Integer;
numBlocks: Integer;
bd: TChilkatBinData;
i: Integer;

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

sftp := TChilkatSFtp.Create(Self);

// 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.
hostname := 'sftp.example.com';
port := 22;
success := sftp.Connect(hostname,port);
if (success <> 1) then
  begin
    Memo1.Lines.Add(sftp.LastErrorText);
    Exit;
  end;

// 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
  begin
    Memo1.Lines.Add(sftp.LastErrorText);
    Exit;
  end;

// After authenticating, the SFTP subsystem must be initialized:
success := sftp.InitializeSftp();
if (success <> 1) then
  begin
    Memo1.Lines.Add(sftp.LastErrorText);
    Exit;
  end;

// 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.)
handle := sftp.OpenFile('big.zip','writeOnly','createTruncate');
if (sftp.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(sftp.LastErrorText);
    Exit;
  end;

// 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.
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.
fac := TCkFileAccess.Create(Self);

success := fac.OpenForRead(localFilePath);
if (success = 0) then
  begin
    sftp.CloseHandle(handle);
    Memo1.Lines.Add(fac.LastErrorText);
    Exit;
  end;

// If we were to split the local file into 128K chunks, how many chunks (blocks) would
// we have, including the last partial block?
blockSize := 131072;
numBlocks := fac.GetNumBlocks(blockSize);
Memo1.Lines.Add('Number of blocks = ' + IntToStr(numBlocks));

bd := TChilkatBinData.Create(Self);
i := 0;
while i < numBlocks do
  begin
    // 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.ControlInterface);
    if (success = 0) then
      begin
        sftp.CloseHandle(handle);
        Memo1.Lines.Add(fac.LastErrorText);
        Exit;
      end;

    // Upload this block to the open remote file.
    success := sftp.WriteFileBd(handle,bd.ControlInterface);
    if (success = 0) then
      begin
        Memo1.Lines.Add(sftp.LastErrorText);
        Exit;
      end;

    // Clear the contents for the next iteration.
    bd.Clear();

    i := i + 1;
  end;

// 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
  begin
    Memo1.Lines.Add(sftp.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success.');
end;