无法打开连接流

Question

您好我正在尝试建立与端口的连接，但每当代码运行时，我都会收到以下错误：thread 1 exc_bad_access

先谢谢

NSString *theTry=@"192.168.3.170:23"; 
    NSInputStream *iStream;
    NSURL *url = [NSURL URLWithString:theTry];

    [iStream initWithURL:url];
    [iStream setDelegate:self];
    [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [iStream open];