DataFlex

Resume an Interrupted FTP Transfer

Demonstrates the RestartNext and PartialTransfer properties, which request that the next transfer resume from existing content and report whether a download was incomplete.

Note: The local paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: For a large transfer over a flaky link, restarting from zero after a drop is wasteful. Setting RestartNext makes the next download continue from the current local file size (and the next upload from the remote size); the flag is consumed by that one transfer and then reset. Afterward PartialTransfer tells you whether the download got only part of the file — the signal to set RestartNext again and resume once more.

Chilkat DataFlex Downloads

Download Chilkat for DataFlex

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFtp
    String sTemp1
    Boolean bTemp1

    Move False To iSuccess

    Get Create (RefClass(cComChilkatFtp2)) To hoFtp
    If (Not(IsComObjectCreated(hoFtp))) Begin
        Send CreateComObject of hoFtp
    End

    Set ComHostname Of hoFtp To "ftp.example.com"
    Set ComUsername Of hoFtp To "myFtpLogin"

    //  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.
    Set ComPassword Of hoFtp To "myPassword"

    Get ComConnect Of hoFtp To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFtp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  RestartNext requests that the NEXT transfer resume from existing content rather than starting
    //  over.  It is consumed by that transfer and then automatically reset.
    Set ComRestartNext Of hoFtp To True

    //  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
    //  the current local file size.
    Get ComGetFile Of hoFtp "public_html/bigfile.zip" "qa_output/bigfile.zip" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFtp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  PartialTransfer indicates whether the most recent download received some, but not all, of the
    //  remote file -- distinguishing a mid-transfer failure from other outcomes.
    Get ComPartialTransfer Of hoFtp To bTemp1
    If (bTemp1) Begin
        Showln "Only part of the file was received; another resume may be needed."
    End
    Else Begin
        Showln "The file was fully received."
    End

    Get ComDisconnect Of hoFtp To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFtp To sTemp1
        Showln sTemp1
        Procedure_Return
    End



End_Procedure