Port

An internet term.

A software 'port' is a bit like channel on television. With televison, you tune in to the right channel in order to get the programme you want.

With the internet, 'ports' are used to connect your computer to a service running on a distant server.

The way it works is that an application running on a server is constantly 'listening' for requests coming in on their assigned 'port'. For example a web server often uses Port 80 to listen for web page requests An FTP (File Transfer Protocol) application will be listening on Port 21 for file transfer requests. A single server can have many applications running at the same time. Each one, listening to their own ports.

One problem with ports is that Firewalls often block them because they are a security risk.

If you are unlucky enough to have your computer infected with some malware such as a spambot, that spambot will try to use a spare port to connect to their master server for instructions. This is why Firewalls block unrecognised ports.

There are about 65,000 ports available on a server, the first 1000 or so have recommended common uses.

There are also 'Hardware Ports' that are physical plugs and sockets on your computer. For example the 'serial port' and the 'Parallel Port'.

2020-10