Ports

The following command will list TCP port 80 connections.

lsof -i tcp:80

The following command will list all IP connections.

netstat -aon

For list of ports registered with IANA Click Here

The port numbers are divided into three ranges.

• The Well Known Ports are those in the range 0–1023. On Unix-like operating systems, opening a port in this range to receive incoming connections requires administrative privileges or possessing of CAP_NET_BIND_SERVICE capability.
  The Registered Ports are those in the range 1024–49151.
• The Dynamic and/or Private Ports are those in the range 49152–65535. Randomly chosen port numbers out of this range are called ephemeral ports. These ports are not permanently assigned to any publicly defined application.
• IANA does not enforce this; it is simply a set of recommended uses. Sometimes ports may be used for different applications or protocols than their official IANA designation. This misuse may be, for example, by a Trojan horse, or alternatively by a commonly used program that did not get an IANA registered port or port range.