Lua

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 Lua Downloads

Download Chilkat for Lua

Lua

local chilkat = require("chilkat")

local ftp = chilkat.Ftp2.new()

ftp.hostname = "ftp.example.com"
ftp.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.password = "myPassword"

local success = ftp:connect()
if not success then
    print(ftp.last_error_text)
    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.
ftp.restart_next = true

-- Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
-- the current local file size.
success = ftp:get_file("public_html/bigfile.zip", "qa_output/bigfile.zip")
if not success then
    print(ftp.last_error_text)
    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.
if ftp.partial_transfer then
    print("Only part of the file was received; another resume may be needed.")
else
    print("The file was fully received.")
end

success = ftp:disconnect()
if not success then
    print(ftp.last_error_text)
    return
end