Port 981 Unassigned - System Port

Port 981 is a System Port. Transport Protocol , Port 981 Service Name , Service Name Description: Unassigned.

Port	Protocol	Description	Source
981		Unassigned	IANA
981	TCP	SofaWare Technologies Remote HTTPS management for firewall devices running embedded Check Point FireWall-1 software,Unofficial	wikipedia
981	TCP UDP	Mac OS X RPC-based services, Used by NetInfo, for example	Apple.com

Port	Service Name	Description
504	citadel	citadel
597	ptcnameservice	PTC Name Service
1627	t128-gateway	T.128 Gateway
1773	kmscontrol	KMSControl
1944	close-combat	close-combat
2819	fc-faultnotify	FC Fault Notification
3090	stss	Senforce Session Services
3175	t1-e1-over-ip	T1_E1_Over_IP
3517	802-11-iapp	IEEE 802.11 WLANs WG IAPP
4289	vrml-multi-use	VRML Multi User Systems

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