Well-Known Ports
TCP/UDP ports 0 to 1023, reserved by IANA for standardised services like HTTP (80), HTTPS (443), and SSH (22).
Well-known ports are TCP and UDP ports in the range 0 to 1023, reserved by IANA for standardised services. Binding to a well-known port traditionally requires root or CAP_NET_BIND_SERVICE on Unix. Familiar assignments include 22 (SSH), 25 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS), 587 (Submission), 993 (IMAPS). Ports 1024 to 49151 are registered (assigned but not as tightly controlled), and 49152 to 65535 are ephemeral (used by clients for outbound connections). IANA publishes the canonical assignment list.