UDPPorts

UDP ports are numeric identifiers used by the User Datagram Protocol to deliver datagrams to the correct application process on a host. Each UDP datagram includes a source port and a destination port, enabling demultiplexing at the receiving end. Together with IP addresses, ports provide a separate addressing space for each active conversation.

Port numbers are 16-bit values, ranging from 0 to 65535. Port 0 is reserved and typically not used by applications. The ports are commonly grouped into three ranges: well-known ports 0–1023, registered ports 1024–49151, and dynamic or private ports 49152–65535. Well-known ports identify widely used services (for example, DNS on 53, HTTP on 80, HTTPS on 443). Registered ports are assigned for specific applications, while dynamic ports are often allocated by the operating system for client-side communications.

UDP is connectionless and provides no guaranteed delivery, ordering, or integrity beyond the UDP checksum. A UDP server binds to a specific port to receive datagrams addressed to that port; a client uses a source port on its socket, typically from the ephemeral range, to receive responses.

Common UDP-based services include DNS (port 53), SNMP (161/162), DHCP (67/68), NTP (123), and TFTP (69). Applications may implement their own reliability mechanisms atop UDP or rely on UDP for real-time or low-latency communications.

Security and network management: UDP traffic can be filtered by firewalls; NAT may complicate inbound connectivity; UDP is often subject to amplification attacks. Best practices include closing unused ports, applying access controls, rate limiting, and using security protocols such as DTLS or IPsec for protection where needed.