Do you want to check if an NTP server is alive and responding to NTP queries? Do you need to manually check an NTP server to see if the clock is correct? Try using ntpdate from a linux CLI to query the NTP server.
$ ntpdate -q pool.ntp.org
server 126.96.36.199, stratum 2, offset 1.552116, delay 0.06792
server 188.8.131.52, stratum 2, offset 1.556884, delay 0.11574
server 184.108.40.206, stratum 2, offset 1.569006, delay 0.11952
server 220.127.116.11, stratum 2, offset 1.542965, delay 0.11389
19 Apr 21:30:06 ntpdate: step time server 18.104.22.168 offset 1.552116 sec
The -q switch says to query only and not set the time. With this command you can query an NTP server and it will return the date it has set.