6590 Unassigned - User Port

6590 is a User Port. Transport Protocol , 6590 Service Name , Service Name Description: Unassigned.

Port	Protocol	Service Name	Description	Source
6590			Unassigned	IANA

Port	Service Name	Description
1022	exp2	RFC3692-style Experiment 2
1388	objective-dbc	Objective Solutions DataBase Cache
1637	islc	ISP shared local data control
4373	remctl	Remote Authenticated Command Service
5192	aol-2	AmericaOnline2
5414	statusd	StatusD
5453	surebox	SureBox
5606		Unassigned
5662		Unassigned
6656	emgmsg	Emergency Message Control Service

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