PowerShell

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 PowerShell Downloads

Download Chilkat for PowerShell

PowerShell

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

$ftp = New-Object Chilkat.Ftp2

$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"

$success = $ftp.Connect()
if ($success -eq $false) {
    $($ftp.LastErrorText)
    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.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 -eq $false) {
    $($ftp.LastErrorText)
    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.PartialTransfer) {
    $("Only part of the file was received; another resume may be needed.")
}
else {
    $("The file was fully received.")
}

$success = $ftp.Disconnect()
if ($success -eq $false) {
    $($ftp.LastErrorText)
    exit
}