657 RMC - System Port | Service Name:rmc

657 is a System Port. Transport Protocol TCP UDP , 657 Service Name rmc, Service Name Description: RMC.

Port	Protocol	Service Name	Description	Source
657	TCP UDP	rmc	RMC	IANA
657	TCP UDP		IBM RMC (Remote monitoring and Control) protocol, used by System p5 AIX Integrated Virtualization Manager (IVM)and Hardware Management Console to connect managed logical partitions (LPAR) to enable dynamic partition reconfiguration,Official	wikipedia
657	TCP UDP		Mac OS X RPC-based services, Used by NetInfo, for example	Apple.com
657	TCP UDP	rmc	RMC	bekkoame

Port	Service Name	Description
1101	pt2-discover	PT2-DISCOVER
1345	vpjp	VPJP
2138	unbind-cluster	UNBIND-CLUSTER
2398	orbiter	Orbiter
3475	genisar-port	Genisar Comm Port
3902	nimaux	NIMsh Auxiliary Port
4509		Unassigned
4840	opcua-tcp	OPC UA TCP Protocol
5060	sip	SIP
6765		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