Port 273 Unassigned - System Port

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

Port	Protocol	Service Name	Description	Source
273			Unassigned	IANA

Port	Service Name	Description
1040	netarx	Netarx Netcare
1127	kwdb-commn	KWDB Remote Communication
1400	cadkey-tablet	Cadkey Tablet Daemon
2052	clearvisn	clearVisn Services Port
2091	prp	PRP
2738	ndl-tcp-ois-gw	NDL TCP-OSI Gateway
3017	event-listener	Event Listener IANA assigned this well-formed service name as a replacement for "event_listener".
3439	hri-port	HRI Interface Port
4254	vrml-multi-use	VRML Multi User Systems
4593	ipt-anri-anri	IPT (ANRI-ANRI)

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