ping用來檢查網路是否通暢或者網路連線速度的命令
telnet是用來探測指定ip是否開放指定埠

用法例項：

ping www.baidu.com

結果：
PING www.a.shifen.com (14.215.177.39) 56(84) bytes of data.
64 bytes from 14.215.177.39: icmp_seq=1 ttl=128 time=6.77 ms
64 bytes from 14.215.177.39: icmp_seq=2 ttl=128 time=7.96 ms
64 bytes from 14.215.177.39: icmp_seq=3
 
 ttl=128 time=6.56 ms
64 bytes from 14.215.177.39: icmp_seq=4 ttl=128 time=8.17 ms
64 bytes from 14.215.177.39: icmp_seq=5 ttl=128 time=6.97 ms
64 bytes from 14.215.177.39: icmp_seq=6 ttl=128 time=8.44 ms
64 bytes from 14.215.177.39: icmp_seq=7 ttl=128 time=6.90 ms
64 bytes from 14.215.177.39: icmp_seq=8
 
 ttl=128 time=7.39 ms
^C
--- www.a.shifen.com ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7642ms
rtt min/avg/max/mdev = 6.567/7.400/8.442/0.667 ms

telnet www.baidu.com 80

結果：
Trying 14.215.177.38...
Connected to www.baidu.com.
Escape character is '^]'.