Cocoa uploader for LetsCrate

uploader.m

NSURL *url = [NSURL URLWithString:@"https://api.letscrate.com/1/files/upload.json"];
    NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
    [req setHTTPMethod:@"POST"];
    
    NSString* authString = [[[NSString stringWithFormat:@"%@:%@", @"LOGIN", @"PASSWORD"] dataUsingEncoding:NSUTF8StringEncoding] base64Encoding];
	authString = [NSString stringWithFormat: @"Basic %@", authString];
	[req setValue:authString forHTTPHeaderField:@"Authorization"];
    
    NSString *boundary = @"0xKhTmLbOuNdArY";
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
    [req setValue:contentType forHTTPHeaderField:@"Content-type"];
    
    NSString *imagePath = [NSString stringWithFormat:@"%@/%@", directory, filename];
    NSData *imageData = [NSData dataWithContentsOfFile:imagePath options:0 error:nil];
    
    //adding the body:
    NSMutableData *postBody = [NSMutableData data];
    [postBody appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[@"Content-Disposition: form-data; name=\"crate_id\"\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[[NSString stringWithFormat:@"%d", crateId] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"file\"; filename=\"a.png\"\r\n\r\n", filename] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:imageData];
    [postBody appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [req setHTTPBody:postBody];
    [req setValue:[NSString stringWithFormat:@"%d", [postBody length]] forHTTPHeaderField:@"Content-length"];
    [req setTimeoutInterval:5];

    NSURLResponse* response = nil;
	NSError* error = nil;
	NSData* reply = [NSURLConnection sendSynchronousRequest:req returningResponse:&response error:&error];