UDP/123 being a IANA-assigned port, it cannot be used by any other legitimate application: the Official IANA port assignment page states: Assigned ports both System and User ports SHOULD NOT be used without or prior to IANA registration.

Port 123. 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. Official : 20 Implementations send and receive timestamps using the User Datagram Protocol (UDP) on port number 123. They can also use broadcasting or multicasting, where clients passively listen to time updates after an initial round-trip calibrating exchange. Mar 30, 2016 · Guaranteed communication over TCP port 123 is the main difference between TCP and UDP. UDP port 123 would not have guaranteed communication as TCP. UDP on port 123 provides an unreliable service and datagrams may arrive duplicated, out of order, or missing without notice. UDP/123 being a IANA-assigned port, it cannot be used by any other legitimate application: the Official IANA port assignment page states: Assigned ports both System and User ports SHOULD NOT be used without or prior to IANA registration. UDP (User Datagram Protocol) is a communications protocol that is primarily used for establishing low-latency and loss-tolerating connections between applications on the internet. It speeds up transmissions by enabling the transfer of data before an agreement is provided by the receiving party. To use Nmap to scan a specific port use the -p flag to define the port followed by the -sU flag to enable UDP scan before specifying the target, to scan LinuxHint for the 123 UDP NTP port run: # UDP scan works by sending a UDP packet to every targeted port. For most ports, this packet will be empty (no payload), but for a few of the more common ports a protocol-specific payload will be sent. Based on the response, or lack thereof, the port is assigned to one of four states, as shown in Table 5.3.

TroubleshootingNTP < Support < NTP

tcpdump: Learning how to read UDP packets - DZone Big Data The last three lines of this output detail the IP header, UDP header and the data in the packet. The following diagram is quite useful for understanding what each part of the IP header is defining NTP responses blocked, even though allowed through policy Aug 21, 2018

May 08, 2019

How to open a udp port in windows 10 - Microsoft Community Jun 14, 2018 Solved: iTunes Home Sharing with Windows … - Apple Community Jul 11, 2014 UDP Port Scanner, Online UDP Port Scan, UDP Port Scanning UDP Port Scanner. With this online UDP port scanner you can scan an IP address for open UDP ports. Use this UDP port scan tool to check what services (dns, tftp, ntp, snmp, mdns, upnp) are running on your server, test if your firewall is working correctly, view open UDP ports. NTP and 123/UDP attack? - LinuxQuestions.org