4502 A25 (FAP-FGW) - User Port | Service Name:a25-fap-fgw

4502 is a User Port. Transport Protocol SCTP , 4502 Service Name a25-fap-fgw, Service Name Description: A25 (FAP-FGW).

Port	Protocol	Service Name	Description	Source
4502	SCTP	a25-fap-fgw	A25 (FAP-FGW)	IANA
4502	TCP		Microsoft Silverlight connectable ports under non-elevated trust,Official	wikipedia

Port	Service Name	Description
775	entomb
899		Unassigned
1533	virtual-places	Virtual Places Software
2718	pn-requester2	PN REQUESTER 2
3683	bmc-ea	BMC EDV/EA
4234	vrml-multi-use	VRML Multi User Systems
4620		Unassigned
4682	finisar	finisar
6364		Unassigned
7044		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