If it comes to an exchange of data between several client server applications, it is vital for the operating system to channel the data packages to ensure a proper delivery.
The channels in which the data packages are bundled are called ports and part of a network address.
Since ports are described with 16bit we can find 65535 different software ports on a computer.
These ports are categorized into:
– 0 to 1023 = Well-known Ports also called system ports
– 1024 to 49151 = Registered Ports also called user ports
– 49252 to 65535 = Dynamic/Private Ports
If data is exchanged using the http-protocol the port 80 is used for example.
In order to increase security within a network it is wise to close all ports that are not used.
This can be done by a firewall.
Some more well known software ports are:
21 – for FTP up- and download
25 – SMTP – to sent e-mails (similar to port 465)
110 – POP3 – to receive e-mails from an e-mail server