Hello,
You can use ntpclient to query NTP server, for example:
ntpclient -c 1 -h 0.lt.pool.ntp.org
You should see a single line printed like
36765 4980.373 1341.0 39.7 956761.4 839.2 0
Column headers explanation are according to http://doolittle.icarus.com/ntpclient/HOWTO
1. day since 1900
2. seconds since midnight
3. elapsed time for NTP transaction (microseconds)
4. internal server delay (microseconds)
5. clock difference between your computer and the NTP server (microseconds)
6. dispersion reported by server (microseconds)
7. your computer's adjtimex frequency (ppm * 65536)
To see if NTP server is being queried you can use tcpdump command:
tcpdump -n -i any dst port 123
Query:
07:42:02.208563 IP your.public.ip.123 > 92.243.6.5.123: NTPv3, Client, length 48
Reply:
07:42:02.302573 IP 92.243.6.5.123 > your.public.ip.123: NTPv3, Server, length 48
-n: Do not resolve domain name
-i: Interface, in this case any interface
dst port 123: filter packets with destination port 123