Sync.m

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setHTTPMethod:@"GET"];
NSString *url = @"http://localhost:5000/api/updates/";
if(checksum){
    url = [NSString stringWithFormat:@"%@?checksum=%@", url, checksum];
}
[request setURL:[NSURL URLWithString:url]];

[[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *err) {
    NSInteger statusCode = [(NSHTTPURLResponse *)response statusCode];

    if (statusCode == 304) {
        //no database update available
        return;
    }else if(statusCode == 200){
        //updated database
        if(initialSync){
            [data writeToFile:@"database.db" atomically:YES];
        }else{
            [data writeToFile:@"updated.db" atomically:YES];
        }
    }

}] resume];