30 Unassigned - System Port

30 is a System Port. Transport Protocol TCP UDP , 30 Service Name , Service Name Description: Unassigned.

Port	Protocol	Description	Source
30	TCP UDP	Unassigned	IANA
30	TCP	Agent 40421	anti-trojan
30		Agent 40421	simovits.com
30	TCP	Agent 40421	bekkoame
30	TCP UDP	Unassigned	bekkoame

Port	Service Name	Description
1902	fjicl-tep-b	Fujitsu ICL Terminal Emulator Program B
2851	webemshttp	webemshttp
3240	triomotion	Trio Motion Control Port
3426	arkivio	Arkivio Storage Protocol
4126	ddrepl	Data Domain Replication Service
4830		Unassigned
4848	appserv-http	App Server - Admin HTTP
6147	montage-lm	Montage License Manager
6183		Unassigned
6221		Unassigned

A port is an endpoint of communication in an operating system. While the term is also used for hardware devices, in software it is a logical construct that identifies a specific process or a type of service.

Port numbers are assigned in various ways, based on three ranges: System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports (49152-65535);

The Well Known Ports are assigned by the IANA and on most systems can only be used by system (or root) processes or by programs executed by privileged users. Ports are used in the TCP [RFC793] to name the ends of logical connections which carry long term conversations. For the purpose of providing services to unknown callers, a service contact port is defined. This list specifies the port used by the server process as its contact port. The contact port is sometimes called the "well-known port". To the extent possible, these same port assignments are used with the UDP [RFC768]. The range for well-known ports managed by the IANA is 0-1023.
DYNAMIC AND/OR PRIVATE PORTS Registered Ports are those from 1024 through 49151.
The Dynamic and/or Private Ports are those from 49152 through 65535