561 - System Port | Service Name:monitor

561 is a System Port. Transport Protocol TCP , 561 Service Name monitor, Service Name Description: .

Port	Protocol	Service Name	Description	Source
561	TCP	monitor		IANA
561	UDP	monitor		IANA
561	UDP		monitor,Official	wikipedia
561	TCP UDP	monitor		bekkoame

Port	Service Name	Description
3256	cpqrpm-agent	Compaq RPM Agent Port
3458	d3winosfi	D3WinOSFI
4605		Unassigned
5216		Unassigned
5367		Unassigned
6916		Unassigned
7333	swx	The Swiss Exchange
7708	scinet	scientia.net
8034	vantronix-mgmt	.vantronix Management
8139		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