iOS basic FTP setup; Read and Write Stream

问题:

I'm attempting to create an iOS 5 app with some very basic FTP functionality and need some guidance. It will be connecting to a device on a local network and performing read/write actions with .dat/txt files. I've done some searching for the past few days and have seen various recommendations but nothing simple enough that I can pick up and quickly modify for my personal use.

My questions are these:

1. Are there any tutorials/sample code that you could recommend to me?
2. What frameworks and classes should I be working with for basic read/write operations?

Lastly, I should mention that I have given a considerable amount of time to analyzing the SimpleFTPSample from Apple but the sample code is giving "Connection Failure" and "Stream Open Error" notices for each example, so I'm a bit wary of its usefulness.

Forgive me if this has been answered elsewhere. All of the related posts have pieces of the answer I need, but not the whole thing. Thank you in advance!

EDIT for clarity: A well-defined example or step-by-step tutorial is what I would really like. My own Google searches have turned up nothing and I am desperately in need of some guidance here.

UPDATE: I posted this question long ago but have continued using the FTPHelper mentioned in the accepted answer. I recently brushed the dust off the old project and realized there was a minor memory leak in FTPHelper's fetch function that can be an app-killer if called repeatedly. If anybdy stumbles across this question and chooses to use FTPHelper, be sure to add the CFRelease line seen in the code below.

- (void) fetch: (NSString *) anItem
{
    if (!self.uname || !self.pword) COMPLAIN_AND_BAIL(@"Please set user name and password first");
    if (!self.urlString) COMPLAIN_AND_BAIL(@"Please set URL string first");

    NSString *ftpRequest = [NSString stringWithFormat:@"%@/%@", self.urlString, [anItem stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
/*  CFShow(ftpRequest); */
    NSString *writepath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
    self.filePath = [writepath stringByAppendingPathComponent:anItem];
    CFURLRef writeURL = CFURLCreateFromFileSystemRepresentation (NULL, (const UInt8 *) [writepath UTF8String], [writepath length], NO); 
    MySimpleDownload((CFStringRef)ftpRequest, writeURL, (CFStringRef) self.uname, (CFStringRef)self.pword);
    CFRelease(writeURL);//ADD THIS LINE TO FIX MEMORY LEAK 
}

回答1:

The SimpleFTPSample app is running perfect, probably there is an issue that you can't see. What I can recommend you (except Apple's example) is to check THIS example which contains a helper class for all basic FTP operations. One thing to be aware of is iOS 5 ARC. Both Apple's example and the one I linked are for older iOS versions.

There are basically 2 ways to use them in iOS 5 - by telling the compiler to not use ARC by adding -fno-objc-arc flag in [Your project] -> TARGETS -> [Your app] -> Build Phases -> Compile Sources -> [Your file], or by using the built-in tool in Xcode for converting to ARC.

I personally have tested only the first method and it works for me.

If this does not help you I can write an example, but unfortunately today I am very busy.

UPDATED:

The basic mechanism is to use [FTPHelper list:THE_FTP_URL] to list the content of a folder, then create one list with the content and depending on the type (file or folder) download using [FTPHelper download: THE_FTP_URL_WITH_THE_FILENAME_FROM_LISTING]. From here you have to implement

- (void) downloadFinished
{
    //do the reading depending on the file type
    NSData *data = [NSData dataWithContentsOfFile:[FTPHelper sharedInstance].filePath];
}

The uploading is achieved in a similar way - using [FTPHelper upload:FILE_TO_UPLOAD] with a file from the filesystem.

回答2:

There are many libraries which you could use and they are working great. :)

For example:

http://www.chilkatsoft.com/ftp-objc.asp

http://code.google.com/p/ios-ftp-server/

I recommend using them, because coding one by yourself would take a lot of time :) One thing to remember, as o15a3d4l11s2 said, is to be aware of ARC. If you use it don't forget to add build flags to libraries which aren't ARC.