273 Unassigned - System Port

273 is a System Port. Transport Protocol , 273 Service Name , Service Name Description: Unassigned.

Port	Protocol	Service Name	Description	Source
273			Unassigned	IANA

Port	Service Name	Description
412	synoptics-trap	Trap Convention Port
1149	bvtsonar	BlueView Sonar Service
2146	lv-not	Live Vault Admin Event Notification
2923	wta-wsp-wtp-s	WTA-WSP-WTP-S
3184	apogeex-port	ApogeeX Port
3920	exasoftport1	Exasoft IP Port
4332		Unassigned
5654		Unassigned
6087	ldss	Local Download Sharing Service
7353	swx	The Swiss Exchange

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