Network - Port (Computer networking)

> NetWork

1 - About

A port (Computer networking) is a network interface.

Both TCP and UDP protocols support ports (65536 max) that programs can choose to bind to.

Port allows programs to run concurrently on one IP address.

Most programs have default ports that are most often used.

For example, HTTP servers commonly use TCP port 80. When a port accepts a connection, it can be assumed that the commonly bound program is running

The reason for having ports is that virtually all modern computers support multitasking. Thus, on a typical computer, there will be multiple programs which need to contact other programs on other computers over the network all at the same time. Ports enable multiple programs to share a single physical network connection simultaneously, as opposed to having only one program using the connection for a long period of time.


3 - Number

The port number is the unique port identifier within a ip address

4 - Range

Port numbers have three ranges:

  • System Ports (0-1023),
  • User Ports (1024-49151),
  • and the Dynamic and/or Private Ports (49152-65535);

The difference uses of these ranges is described in RFC 6335

5 - Internet Protocol

In the context of the Internet Protocol, a port is associated with an IP address of the host, as well as the type of protocol used for communication.

A specific port is identified by:

  • its number, commonly known as the port number,
  • the IP address with which it is associated,
  • and the protocol used for communication (TCP or UDP)

(same as Network - (Internet) Socket ???)


6 - Well known port numbers

Service Name and Transport Protocol Port Number Registry defines the well known port numbers of the Internet Assigned Numbers Authority (IANA) - responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources.

7 - State

8 - Open

9 - Forwarding

10 - Documentation / Reference