UDPpoort

UDPpoort is the numeric port used by the User Datagram Protocol (UDP) to demultiplex datagrams to the appropriate application on a host. UDPport numbers are 16-bit values, allowing a range from 0 to 65535. Port 0 is reserved and should not be used by applications; some systems permit binding to port 0 to request an ephemeral port assigned by the operating system. The remaining range is divided into well-known ports (0–1023), registered ports (1024–49151), and dynamic/private ports (49152–65535). Well-known ports are typically associated with widely used services, such as DNS at port 53.

A UDP datagram contains a header with four 16-bit fields: source port, destination port, length, and checksum. The UDP checksum covers the header and payload and helps detect corruption. In IPv4 the checksum is optional in practice, whereas in IPv6 the checksum is mandatory.

UDP is a connectionless protocol. It does not establish or maintain a connection, nor does it guarantee delivery, ordering, or protection against duplicates. This makes UDP lightweight and low-latency, suitable for time-sensitive or multicast/broadcast applications. Applications and higher-layer protocols may provide reliability if needed.

Common uses of UDPport include domain name system queries, DHCP, SNMP, and real-time media or gaming traffic. Clients typically send datagrams to a known destination UDPport, while servers listen on a fixed UDPport. Because UDP is stateless, it interacts with firewalls and Network Address Translation (NAT) differently from TCP, often requiring explicit UDP port openings or techniques such as port forwarding and UDP hole punching for peer-to-peer communication.

See also: UDP, TCP ports, network sockets, firewall considerations.