(Objective-C) Asynchronous FTP Download

The Chilkat FTP component supports asynchronous uploads and downloads. This examples demonstrates doing a download in a background thread. The download is started by calling AsyncGetFileStart. While the download is in progress, your program may do other tasks. You may periodically check the AsyncFinished property to determine when the transfer is finished. The example below provides the remainder of the details.

Download: Chilkat Cocoa Objective-C Libraries

NSMutableString *strOutput = [NSMutableString stringWithCapacity:1000];

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

BOOL success;

//  Any string unlocks the component for the 1st 30-days.
success = [ftp UnlockComponent: @"Anything for 30-day trial"];
if (success != YES) {
    [strOutput appendString: ftp.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

ftp.Hostname = @"ftp.myftpserver.com";
ftp.Username = @"test";
ftp.Password = @"test";

//  Connect and login to the FTP server.
success = [ftp Connect];
if (success != YES) {
    [strOutput appendString: ftp.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

NSString *localFilename;
localFilename = @"hamlet.xml";
NSString *remoteFilename;
remoteFilename = @"hamlet.xml";

//  Begin the download in a background thread.
//  Only 1 background upload or download may be active at any time.
//  (per instance of an FTP object)
success = [ftp AsyncGetFileStart: remoteFilename localFilename: localFilename];
if (success != YES) {
    [strOutput appendString: ftp.LastErrorText];
    [strOutput appendString: @"\n"];
    self.mainTextField.stringValue = strOutput;
    return;
}

//  The application is now free to do anything else
//  while the file is downloading.
//  For this example, we'll simply sleep and periodically
//  check to see if the transfer if finished.  While checking
//  however, we'll report on the progress in both number
//  of bytes tranferred and performance in bytes/second.
while (ftp.AsyncFinished != YES) {

    [strOutput appendFormat: @"%d bytes received\n",[ftp.AsyncBytesReceived intValue]];
    [strOutput appendFormat: @"%d bytes per second\n",[ftp.DownloadRate intValue]];

    //  Sleep 1 second.
    [ftp SleepMs: [NSNumber numberWithInt: 1000]];

}

[strOutput appendFormat: @"%d total bytes received\n",[ftp.AsyncBytesReceived intValue]];
[strOutput appendFormat: @"%d final bytes per second\n",[ftp.DownloadRate intValue]];

//  Did the download succeed?
if (ftp.AsyncSuccess == YES) {
    [strOutput appendString: @"File Downloaded!"];
    [strOutput appendString: @"\n"];
}
else {
    //  The error information for asynchronous ops
    //  is in AsyncLog as opposed to LastErrorText
    [strOutput appendString: ftp.AsyncLog];
    [strOutput appendString: @"\n"];
}

[ftp Disconnect];


self.mainTextField.stringValue = strOutput;