CkPython

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.

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CkPython

import sys
import chilkat

success = False

ftp = chilkat.CkFtp2()

ftp.put_Hostname("ftp.example.com")
ftp.put_Username("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.
ftp.put_Password("myPassword")

success = ftp.Connect()
if (success == False):
    print(ftp.lastErrorText())
    sys.exit()

#  RestartNext requests that the NEXT transfer resume from existing content rather than starting
#  over.  It is consumed by that transfer and then automatically reset.
ftp.put_RestartNext(True)

#  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
#  the current local file size.
success = ftp.GetFile("public_html/bigfile.zip","qa_output/bigfile.zip")
if (success == False):
    print(ftp.lastErrorText())
    sys.exit()

#  PartialTransfer indicates whether the most recent download received some, but not all, of the
#  remote file -- distinguishing a mid-transfer failure from other outcomes.
if (ftp.get_PartialTransfer()):
    print("Only part of the file was received; another resume may be needed.")
else:
    print("The file was fully received.")

success = ftp.Disconnect()
if (success == False):
    print(ftp.lastErrorText())
    sys.exit()