Delphi DLL

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. Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
sftp: HCkSFtp;
hostname: PWideChar;
port: Integer;
handle: PWideChar;
localFilePath: PWideChar;
fac: HCkFileAccess;
blockSize: Integer;
numBlocks: Integer;
bd: HCkBinData;
i: Integer;

begin
success := False;

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

sftp := CkSFtp_Create();

// Set some timeouts, in milliseconds:
CkSFtp_putConnectTimeoutMs(sftp,5000);
CkSFtp_putIdleTimeoutMs(sftp,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 := CkSFtp_Connect(sftp,hostname,port);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    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 := CkSFtp_AuthenticatePw(sftp,'myLogin','myPassword');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

// After authenticating, the SFTP subsystem must be initialized:
success := CkSFtp_InitializeSftp(sftp);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    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 := CkSFtp__openFile(sftp,'big.zip','writeOnly','createTruncate');
if (CkSFtp_getLastMethodSuccess(sftp) <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    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 := CkFileAccess_Create();

success := CkFileAccess_OpenForRead(fac,localFilePath);
if (success = False) then
  begin
    CkSFtp_CloseHandle(sftp,handle);
    Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
    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 := CkFileAccess_GetNumBlocks(fac,blockSize);
Memo1.Lines.Add('Number of blocks = ' + IntToStr(numBlocks));

bd := CkBinData_Create();
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 := CkFileAccess_ReadBlockBd(fac,i,blockSize,bd);
    if (success = False) then
      begin
        CkSFtp_CloseHandle(sftp,handle);
        Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
        Exit;
      end;

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

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

    i := i + 1;
  end;

// Close the local file.
CkFileAccess_FileClose(fac);

// -----------------------------------------------------------------------------
// 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 := CkSFtp_CloseHandle(sftp,handle);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

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

CkSFtp_Dispose(sftp);
CkFileAccess_Dispose(fac);
CkBinData_Dispose(bd);

end;