ping 127.0.0.1 输出error type 8 received, error code 0

```bash
>> sudo ./ping 127.0.0.1

PING 127.0.0.1 (127.0.0.1).
error type 8 received, error code 0 
60 bytes from 127.0.0.1 (127.0.0.1): icmp_seq=0 ttl=64 time=0.00 ms
Net is online!
```
虽然显示Net is online，但是如果函数中的for循环次数改为1的话，就会输出offline，这种行为是不正确的

```bash
>> sudo ./ping 127.0.0.1

PING 127.0.0.1 (127.0.0.1).
error type 8 received, error code 0 
Net is offline!
```