Why does NSURL POST file upload task fail to upload to web server

Question

I am trying to upload a text file to a web server from an iOS application. I have written an objective C method to handle the upload request and a PHP file to handle the POST request at the server. I have also written a small HTML page to test the upload from a browser (which is working fine using the same PHP file). When the iOS App runs it should upload a text file (which is empty ie 0 bytes in size) to a specified folder on the web server, and although the debug window shows the response as success(200) the file is not uploaded.

Here is the Objective C method

    + (void)fileUpload{
        NSString *localFilePath = [self GetTokenFilePath];
        NSURL *localFile = [NSURL fileURLWithPath:localFilePath];
        NSData *data = [[NSData alloc] initWithContentsOfFile:localFilePath];
        NSString *filename = [self GetTokenFilename];
        // Set up the body of the POST request.

        // This boundary serves as a separator between one form field and the next.
        // It must not appear anywhere within the actual data that you intend to
        // upload.
        NSString * boundary = @"---------------------------14737809831466499882746641449";

        // Body of the POST method
        NSMutableData * body = [NSMutableData data];
    
        // The body must start with the boundary preceded by two hyphens, followed
        // by a carriage return and newline pair.
        //
        // Notice that we prepend two additional hyphens to the boundary when
        // we actually use it as part of the body data.
        //
        [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary]     dataUsingEncoding:NSUTF8StringEncoding]];
    
        // This is followed by a series of headers for the first field and then
        // TWO CR-LF pairs. set tag-name to submit upload
        [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data;      name=\"file\"; filename=\"%@.txt\"\r\n", filename] dataUsingEncoding:NSUTF8StringEncoding]];

        [body appendData:[@"Content-Type: application/octet-stream\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
        // Next is the actual data for that field (called "tag_name") followed by
        // a CR-LF pair, a boundary, and another CR-LF pair.
        [body appendData:[NSData dataWithData:data]];
    
        // Close the request body with one last boundary with two
        // additional hyphens prepended **and** two additional hyphens appended.
        [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n", boundary]     dataUsingEncoding:NSUTF8StringEncoding]];

    
        // Data uploading task.
        NSURL * url = [NSURL URLWithString:@"https://MY_URL.co.uk/Upload.php"];
        NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];
        NSString * contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
        [request addValue:contentType forHTTPHeaderField:@"Content-Type"];
        request.HTTPMethod = @"POST";
        request.HTTPBody = body;
    
        /*------------------*/
        NSURLSession *session = [NSURLSession sharedSession];
    
        // Create a NSURLSessionUploadTask object to Upload data for a jpg image.
        NSURLSessionUploadTask *task = [session uploadTaskWithRequest:request fromFile:localFile completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        
            if (error == nil) {
                // Upload success.
                NSLog(@"upload file：%@",localFile);
                NSLog(@"upload success：%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
                NSLog(@"upload response：%@",response);
                // Update user defaults to show success on token upload.
                NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
                [defaults setBool:TRUE forKey:@"TOKEN_UPLOAD_SUCCESS"];
            } else {
                // Upload fail.
                NSLog(@"upload error:%@",error);
                NSLog(@"upload response：%@",response);
                // Update user defaults to show success on token upload.
                NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
                [defaults setBool:FALSE forKey:@"TOKEN_UPLOAD_SUCCESS"];
            }
        
        }];
        [task resume];
    
     }

Here is the PHP file I use at the server end

    <?php

    print_r($_POST);
    echo "<br>";

    //phpinfo();

    // file properties
    $file = $_FILES['file'];
    $file_name = $_FILES['file']['name'];
    $file_tmp = $_FILES['file']['tmp_name'];
    $file_size = $_FILES['file']['size'];
    $file_error = $_FILES['file']['error'];
    $file_type = $_FILES['file']['type'];
    echo "File name = ".$file_name."<br>";
    echo "File size = ".$file_size."<br>";
    echo "File error = ".$file_error."<br>";
    //print_r($file);


    //work out the file extension

    $file_ext = explode('.' , $file_name );
    $file_actual_ext = strtolower(end($file_ext));
    echo "File Extension = ".$file_actual_ext."<br>";
    //echo $file_actual_ext;

    $allowed = array('txt', 'csv');
    print_r($allowed);
    echo "<br>";

    if(in_array($file_actual_ext,$allowed)) {
        echo "File type is allowed"."<br>";
        if($file_error === 0) {
            if($file_size <= 1048576) {
                $file_destination = "TokensV11/".$file_name;
                echo "File Destination = ".$file_destination."<br>";
                    if(move_uploaded_file($file_tmp, $file_destination)) {
                        echo "The file has been uploaded sucessfully"."<br>";
                    }else{
                        echo "The file was not moved to destination"."<br>";
                    }
                }else{
                    echo "The file size is too large"."<br>";
                    }
            }else{
                echo "There was an error uploading your file"."<br>";
                }
    }else {
            echo "You cannot upload files of this type or no file was specified"."<br>";
            }

    ?>

Here is the output sample from the debug window in Xcode

2023-07-25 12:39:26.855874+0100 BikerCafe[3036:86717] upload file：file:///Users/stephencox/Library/Developer/CoreSimulator/Devices/5246C453-B5BF-4F6E-B4BD-E5121A382E87/data/Containers/Data/Application/MYFILE.txt
2023-07-25 12:39:28.238222+0100 BikerCafe[3036:86717] upload success：The PHP script has started<br>File name = <br>File size = <br>File error = <br>File Extension = <br>Array
(
    [0] => txt
    [1] => csv
    [2] => png
)
<br>File Destination = TokensV11/<br>
2023-07-25 12:39:30.723756+0100 BikerCafe[3036:86717] upload response：<NSHTTPURLResponse: 0x6000010e7f60> { URL: https://tokens.ukbikercafes.co.uk/TokenUpload.php } { Status Code: 200, Headers {
    "Content-Encoding" =     (
        gzip
    );
    "Content-Type" =     (
        "text/html; charset=UTF-8"
    );
    Date =     (
        "Tue, 25 Jul 2023 11:39:23 GMT"
    );
    Server =     (
        Apache
    );
    "x-powered-by" =     (
        "PHP/7.4.33"
    );
} }

Answer 1

I have managed to figure out my issue using the guidance of the example from this stackoverflow post. Upload multipart image to PHP server from iOS app . I did have to convert the example from Swift to Objective C with a few minor changes to suit my needs but it worked well.