ios - 无法建立与服务器的连接

Question

我必须通过调用 api /api/places来建立与服务器http://sand.com的连接。我将 NSMutableURLRequest 对象用于上述 url 和 Authorization 标头。建立了几次连接，但我没有收到数据，但现在根本没有建立连接，而是多次调用了 didReceiveAuthenticationChallenge。（授权标头设置值是用户名：base64 格式的密码）我哪里出错了？

NSString *urlString =
        [NSString stringWithFormat:@"http://sand.com/api/places",hostURL];
NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:[NSURL       URLWithString:urlString] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:300.0];
[theRequest setValue:@"Basic c3VyYWJoaV9taXNocmE6bWlzaHJhaml2ZQ==" forHTTPHeaderField:@"Authorization"];
[theRequest setHTTPMethod:@"GET"];
NSURLconnections *nuc = [NSURLconnections new];
nuc.delegate = self;
[nuc connectToRequest:theRequest];

- (void)connectToRequest:(NSURLRequest*)theRequest
{
    urlConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    if (urlConnection) 
    { 
      responseData=[NSMutableData data];
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:   (NSURLAuthenticationChallenge *)challenge 
{
   if ([challenge previousFailureCount] == 0)
    {  
       NikeAppDelegate *appDelegate = [[UIApplication sharedApplication]delegate];
    username = appDelegate.username; password = appDelegate.password;
       NSURLCredential *cred = [[NSURLCredential alloc]
                             initWithUser:username
                             password:password
                             persistence:NSURLCredentialPersistenceNone];
       [[challenge sender] useCredential:cred forAuthenticationChallenge:challenge]; 
    }
}