DataFlex

Resume an Interrupted SFTP Download

Demonstrates the Chilkat SFtp.ResumeDownloadFileByName method, which resumes an interrupted download. The first argument is the remote file path and the second is the local file path. Chilkat uses the existing local file size as the remote starting offset.

Note: This example uses relative local paths, which are resolved against the application's current working directory. Absolute local paths may also be used. Supply the paths appropriate to your own environment.

Background: The download counterpart to resuming an upload: it compares the local file size against the remote and fetches only what is missing — a full download if the local file is absent or empty, the remaining bytes appended if it is shorter, and nothing if it is already complete. As with resumed uploads, the check is size-based and assumes the partial file is a correct prefix of the remote file.

Chilkat DataFlex Downloads

Download Chilkat for DataFlex

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoSftp
    Integer iPort
    String sPassword
    String sTemp1

    Move False To iSuccess

    //  Demonstrates the SFtp.ResumeDownloadFileByName method, which resumes an interrupted download.
    //  The 1st argument is the remote file path and the 2nd is the local file path.

    Get Create (RefClass(cComChilkatSFtp)) To hoSftp
    If (Not(IsComObjectCreated(hoSftp))) Begin
        Send CreateComObject of hoSftp
    End

    //  Connect, authenticate, and initialize the SFTP subsystem.
    Move 22 To iPort
    Get ComConnect Of hoSftp "sftp.example.com" iPort To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoSftp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    Move "mySshPassword" To sPassword

    Get ComAuthenticatePw Of hoSftp "mySshLogin" sPassword To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoSftp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComInitializeSftp Of hoSftp To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoSftp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Resume downloading the remote file.  Chilkat uses the existing local file size as the remote
    //  starting offset, so only the remaining bytes are appended.  If the local file is missing or
    //  empty, a normal full download is performed.
    Get ComResumeDownloadFileByName Of hoSftp "subdir/largefile.zip" "qa_output/largefile.zip" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoSftp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Download resumed and completed."

    Send ComDisconnect To hoSftp


End_Procedure