nc -uvz 11.0.19.11 123 //command not found，则yum install nc
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 11.0.19.11:123.
Ncat: UDP packet sent successfully
Ncat: 1 bytes sent, 0 bytes received in 2.02 seconds.
