Objective-C

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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Objective-C

#import <CkoFtp2.h>

BOOL success = NO;

CkoFtp2 *ftp = [[CkoFtp2 alloc] init];

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";

//  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.
ftp.HeartbeatMs = [NSNumber numberWithInt:100];

//  AbortCurrent may be set to true (typically from another thread, or from an AbortCheck
//  callback) to cancel a running operation.  Left false here so nothing is pre-emptively aborted.
ftp.AbortCurrent = NO;

//  LargeFileMeasures (default false) sends a NOOP on the control channel once per minute during
//  a long transfer, keeping the control connection alive while data flows.
ftp.LargeFileMeasures = YES;

success = [ftp Connect];
if (success == NO) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

success = [ftp GetFile: @"public_html/hugefile.iso" localPath: @"qa_output/hugefile.iso"];
if (success == NO) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

NSLog(@"%@",@"Transfer complete.");

success = [ftp Disconnect];
if (success == NO) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}