Port 53 is used for the Domain Name System (DNS), which is a network protocol used for translating human-readable domain names into IP addresses that computers can understand. DNS client applications use the DNS protocol to query and request information from DNS servers, and the server returns the results to the client using the same port. Port 53 is used for both TCP and UDP communication.
- DNS queries use User Datagram Protocol (UDP) because of its low-latency, bandwidth, and resource usage compared to Transmission Control Protocol (TCP)-equivalent queries.
- TCP Port 53 is used for zone transfers and maintaining coherence between the DNS database and the server.
- The TCP protocol should not be used for queries as it gives a lot of information, which is useful to attackers.
- Some organizations or administrators may choose to run their DNS servers on non-standard ports to bypass firewall restrictions, reduce the likelihood of an attack, or for testing purposes. However, non-standard DNS ports are not widely used and are not recommended for general use because they can cause compatibility issues and can make it more difficult for other.
