Internet & Network Ports Reference



		NETWORKING


		
			A network port identifies a logical communication endpoint
			associated with a transport protocol such as TCP or UDP. Ports
			help operating systems and network services distinguish between
			different applications using the same IP address.
		

		
			A port number alone does not prove that a particular service is
			running. Services can be configured to use different ports, and
			firewalls, NAT, routing, and other controls can affect whether
			traffic actually reaches an endpoint.
		


		Common TCP Ports

		

			

				
					
						Port
						Protocol
						Common Association
						Typical Role
					
				

				

					20 TCP FTP Data File Transfer Protocol data connection.
					21 TCP FTP FTP command and control connection.
					22 TCP SSH Secure remote administration and related services.
					23 TCP Telnet Legacy remote terminal protocol.
					25 TCP SMTP Mail transfer.
					53 TCP/UDP DNS Domain Name System communication.
					80 TCP HTTP Traditional unencrypted HTTP traffic.
					110 TCP POP3 Mail retrieval.
					143 TCP IMAP Mail access.
					443 TCP HTTPS HTTP over TLS.
					587 TCP SMTP Submission Mail submission by clients.
					993 TCP IMAPS IMAP over TLS.
					995 TCP POP3S POP3 over TLS.

				

			

		


		Common UDP-Associated Ports

		

			

				
					
						Port
						Common Association
						Typical Role
					
				

				

					53 DNS DNS queries can use UDP, with TCP also used in specific circumstances.
					67 DHCP Server DHCP server-side communication.
					68 DHCP Client DHCP client-side communication.
					123 NTP Network time synchronization.
					161 SNMP Network management and monitoring.
					500 IKE Internet Key Exchange for IPsec.
					514 Syslog Traditional syslog transport association.

				

			

		


		Port Number Ranges

		

			

				
					
						Range
						Classification
						General Description
					
				

				

					
						0–1023
						System / Well-Known
						Ports traditionally associated with widely used services and protocols.
					

					
						1024–49151
						Registered
						Ports commonly registered for particular applications or services.
					

					
						49152–65535
						Dynamic / Private
						Often used for temporary or application-selected connections.
					

				

			

		


		

			A Port Number Does Not Mean a Service Is Open

			
				For communication to succeed, a service normally needs to be
				listening and reachable. Firewalls, NAT, routing, operating
				system policies, service configuration, and network security
				controls can all determine whether traffic reaches the
				intended endpoint.
			

		


		
			
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