77 any private RJE service - System Port

77 is a System Port. Transport Protocol TCP UDP , 77 Service Name , Service Name Description: any private RJE service.

Port	Protocol	Description	Source
77	TCP UDP	any private RJE service	IANA
77		priv-rjs protocol which is considered unsafe by Google Chrome,Unofficial	wikipedia
77	TCP UDP	any private RJE service	bekkoame

Port	Service Name	Description
971		Unassigned
1195	rsf-1	RSF-1 clustering
1789	hello	hello
2250	remote-collab	remote-collab
3118	pkagent	PKAgent
3268	msft-gc	Microsoft Global Catalog
4432	l-acoustics	L-ACOUSTICS management
4777		Unassigned
5675	v5ua	V5UA application port
6313		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