kCFErrorDomainCFNetwork错误-1005 AFNetworking

我有一个单身人士课程:

+(id)sharedClient
{
static HackerNewsClient *__instance;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
    NSURL *url = [NSURL URLWithString:@"http://node-hnapi.herokuapp.com"];
    __instance = [[HackerNewsClient alloc] initWithBaseURL:url];
});

return __instance;
}

在控制器中,我这样称呼它:

 [[HackerNewsClient sharedClient]GET:@"/news"
                         parameters:nil
                            success:^(NSURLSessionDataTask *task, id responseObject) {

                                NSArray *posts = [self parseEpisodeJSONData:responseObject];
                                completion(posts);
                            } failure:^(NSURLSessionDataTask *task, NSError *error) {
                                NSLog(@"ERROR: %@", error);
                            }];

这个创建的URL http://node-hnapi.herokuapp.com/news是一个有效且有效的URL.但是返回的错误消息是

2014-07-08 08:51:15.942 hn[27435:1627947] ERROR: Error Domain=NSURLErrorDomain Code=-1005 "The operation couldn’t be completed. (NSURLErrorDomain error -1005.)" UserInfo=0x10ba2bf70 {NSErrorFailingURLStringKey=http://node-hnapi.herokuapp.com/news, NSErrorFailingURLKey=http://node-hnapi.herokuapp.com/news, _kCFStreamErrorDomainKey=1, _kCFStreamErrorCodeKey=57, NSUnderlyingError=0x10ba22ff0 "The operation couldn’t be completed. (kCFErrorDomainCFNetwork error -1005.)"}

我无法弄清楚导致这个问题的原因.谢谢