110 Post Office Protocol - Version 3 - System Port

110 is a System Port. Transport Protocol TCP UDP , 110 Service Name pop3, Service Name Description: Post Office Protocol - Version 3.

Port	Protocol	Service Name	Description	Source
110	TCP UDP	pop3	Post Office Protocol - Version 3	IANA
110	TCP		Post Office Protocol v3 (POP3),Official	wikipedia
110	TCP		Post Office Protocol (POP3), Mail (for receiving email)	Apple.com
110	TCP		ProMail trojan	emsisoft
110	TCP		ProMail	anti-trojan
110			ProMail trojan	sans.org
110			ADM worm	simovits.com
110	TCP UDP	pop3	Post Office Protocol - Version 3	bekkoame
110	TCP		ProMail trojan	bekkoame
110	TCP		Bancos	bekkoame
110	TCP		Civcat	bekkoame

Port	Service Name	Description
2128	net-steward	Net Steward Control
2643	gte-samp	GTE-SAMP
4980		Unassigned
5170		Unassigned
6244	jeol-nsdtp-4	JEOL Network Services Data Transport Protocol 4
6488	sun-sr-jmx	Service Registry Default JMX Domain
6539		Unassigned
6785	dgpf-exchg	DGPF Individual Exchange
7404		Unassigned
7477		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