Tcl

Monitor, Cancel, and Keep-Alive Long FTP Transfers

Demonstrates the HeartbeatMs, AbortCurrent, and LargeFileMeasures properties, which monitor long operations, allow cancellation, and keep the control connection alive during long transfers.

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: A large transfer blocks for a long time, and these properties make that manageable. HeartbeatMs fires a periodic AbortCheck callback so an application can show progress and remain responsive, and AbortCurrent — set from that callback or another thread — cancels the running operation. LargeFileMeasures addresses a subtler problem: while data flows on the data connection, an idle control connection can be dropped by a firewall, so this sends a periodic NOOP to keep it alive.

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Tcl


load ./chilkat.dll

set success 0

set ftp [new_CkFtp2]

CkFtp2_put_Hostname $ftp "ftp.example.com"
CkFtp2_put_Username $ftp "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.
CkFtp2_put_Password $ftp "myPassword"

#  HeartbeatMs sets how often the AbortCheck event fires during long operations.  The default 0
#  disables it.  A nonzero value lets an application monitor progress and request cancellation.
CkFtp2_put_HeartbeatMs $ftp 100

#  AbortCurrent may be set to 1 (typically from another thread, or from an AbortCheck
#  callback) to cancel a running operation.  Left 0 here so nothing is pre-emptively aborted.
CkFtp2_put_AbortCurrent $ftp 0

#  LargeFileMeasures (default 0) sends a NOOP on the control channel once per minute during
#  a long transfer, keeping the control connection alive while data flows.
CkFtp2_put_LargeFileMeasures $ftp 1

set success [CkFtp2_Connect $ftp]
if {$success == 0} then {
    puts [CkFtp2_lastErrorText $ftp]
    delete_CkFtp2 $ftp
    exit
}

set success [CkFtp2_GetFile $ftp "public_html/hugefile.iso" "qa_output/hugefile.iso"]
if {$success == 0} then {
    puts [CkFtp2_lastErrorText $ftp]
    delete_CkFtp2 $ftp
    exit
}

puts "Transfer complete."

set success [CkFtp2_Disconnect $ftp]
if {$success == 0} then {
    puts [CkFtp2_lastErrorText $ftp]
    delete_CkFtp2 $ftp
    exit
}


delete_CkFtp2 $ftp