Writing file to secure server

I'm trying to write a text file to a secure server .....

-(IBAction) startUpload{
    NSLog(@"Start upload");

    NSString *myString = @开发者_运维技巧"TESTTEXT";
    NSURL *myURL = [NSURL URLWithString:@"ftp://USERNAME:PASSWORD@72.167.1.1/testfile.plist"];

    NSError *error;

    BOOL ok = [myString writeToURL:myURL atomically:NO encoding:NSUTF8StringEncoding error:&error];

    if (!ok) { // if NOT ok
        NSLog(@"error writing to file at %@, %@, %@",myURL,[error localizedFailureReason],[error localizedDescription]);
    }

}

... and all I get is this error message ....

error writing to file at ftp://USERNAME:PASSWORD@72.167.1.1/testfile.plist, (null), The operation couldn’t be completed. (Cocoa error 518.)

All help appreciated

I think FTP is not supported as NSURL,

take a look to this question: NSURL with http:// works fine but with ftp:// not

also take a look to this one

Upload photo to arbitrary FTP with iPhone app

Have a look at s7ftprequest

Description:

This project was inspired by a marvelous lib that I'm using in all my apps that involve network interactions (I can hardly remember one without any): ASIHTTPRequest.

This is the product of composing together ASIHTTPRequest design solutions and SimpleFTPSample techniques.