7573 Unassigned - User Port

7573 is a User Port. Transport Protocol , 7573 Service Name , Service Name Description: Unassigned.

Port	Protocol	Service Name	Description	Source
7573			Unassigned	IANA
7573	UDP		QuickTime Streaming Server	Apple.com

Port	Service Name	Description
992	telnets	telnet protocol over TLS/SSL
2299	pc-telecommute	PC Telecommute
2707	emcsymapiport	EMCSYMAPIPORT
3583	canex-watch	CANEX Watch System
5277		Unassigned
6157		Unassigned
6304		Unassigned
6376		Unassigned
6993		Unassigned
7142		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