I am trying to setup the NTP server on Ubuntu machine. Am breaking my head in this particular issue. Getting an error ntpdate[5005]: no server suitable for synchronization found when doing the command ntppdate. Can anyone please help me out in this? /etc/ntp.conf: server 0.ubuntu.pool.ntp.org server 1.ubuntu.pool.ntp.org server 2.ubuntu.pool.ntp.org server 3.ubuntu.pool.ntp.org Also when I gave command netstat -anltp | grep "LISTEN" tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 1816/dnsmasq tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 939/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1013/cupsd tcp 0 0 127.0.0.1:39558 0.0.0.0:* LISTEN 5529/rsession tcp 0 0 0.0.0.0:902 0.0.0.0:* LISTEN 1275/vmware-authdla tcp 0 0 127.0.0.1:47304 0.0.0.0:* LISTEN 5822/rsession tcp6 0 0 :::80 :::* LISTEN 1400/apache2 tcp6 0 0 :::22 :::* LISTEN 939/sshd tcp6 0 0 ::1:631 :::* LISTEN 1013/cupsd So what should I do so that it listens on 123? If I get output as PORT STATE SERVICE 123/udp open ntp If I give command nmap -p 123 -sU -P0 192.168.36.198, it means UDP is open right? Then why doesn't it show in the command to to show listening ports?