4504 Unassigned - User Port

4504 is a User Port. Transport Protocol , 4504 Service Name , Service Name Description: Unassigned.

Port	Protocol	Service Name	Description	Source
4504			Unassigned	IANA
4504	TCP		Microsoft Silverlight connectable ports under non-elevated trust,Official	wikipedia

Port	Service Name	Description
4064	ice-srouter	Ice Firewall Traversal Service (SSL)
4195		Unassigned
4628		Unassigned
6002	x11	X Window System
6156		Unassigned
6301	bmc-ctd-ldap	BMC CONTROL-D LDAP SERVER IANA assigned this well-formed service name as a replacement for "bmc_ctd_ldap".
6470		Unassigned
6897		Unassigned
7283	genstat	General Statistics Rendezvous Protocol
8083	us-srv	Utilistor (Server)

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