Port 123 is used for Network Time Protocol (NTP) which is used for synchronizing the clocks of computers over a network.
Ports those registered with IANA are shown as official ports. The same port number may be unofficialy used by various services or applications. The official usage are listed separately below its usage may change from time to time.
|Port||Protocol (TCP/UDP)||Title||Description||Port Type|
|Port 123||tcp||ntp||Network Time Protocol||WELL KNOWN PORT|
|Port 123||udp||ntp||Network Time Protocol||WELL KNOWN PORT|
Unofficialy or sometimes with conflict, the same port may be used by different applications.