What Is DNS Server Or Protocol Port Number?
Domain Name System aka DNS is used to match domain names to the IP addresses. DNS is provided over intranet and internet servers with different port numbers.
TCP or UDP
DNS can use both transmission protocols TCP and UDP. But general usage is over UDP protocol because of its simplicity and speed.
TCP Port 53
One of the used DNS port is TCP Port 53. TCP provides stability over DNS resolutions process. With TCP 53 there will be no data loss over network transmission which makes DNS transaction more stable. But this will create some overhead for the server and client because of the TCP behavior.
UDP Port 53
Most known and popular usage protocol of DNS is UDP 53. Most DNS servers uses UDP 53 port which provides simplicity and less resource usage.
DNSSEC Port Number
DNSSEC provides secure DNS transactions which will secure domain name to IP translation secure manner. DNSSEC can use both UDP and TCP 53 ports. But as DNSSEC packets are generally larger than 512 bytes and UDP can transmit a maximum 512 byte TCP protocol is used for DNSSEC. So DNSSEC uses TCP 53 port for communication.