TCP/IP

Ports

Well known port numbers

21 TCP File Transfer Protocol (FTP) control 22 Secure Shell (SSH), secure logins file transfers and port forwarding

Protocols

http

Hyper Text Transfer Protocol, most often found at the beginning of URLs, is used to transfer an user to a web address that is specified via the domain. This uses port 80,

https

A verified, secure version of HTTP. This ensures the user that the website they are on is safe and well protected. This uses port 443.

ftp

File Transfer Protocol. This allows you to download / upload files to a server, for example you would upload your websites pages to your webserver using FTP. FTP uses port 21.

SSH

Secure Shell protocol. This protocol allows remote access to a computer, this could be used to perform admin tasks on a server. You will only have command line access to the computer. SSH is also designed for operating securely over an unsecure network. SSH uses port 22, this was deliberately chosen because it was created to potentially use instead of Telnet or FTP.

telnet

Allows a user to log into a remote computer over the interlinking network. Similar to but predates SSH. Telnet uses port 23.

pop3

Post Office Protocol, version 3. Used to receive incoming emails from an email server. This uses port 110.

smtp

Simple Mail Transfer Protocol. This is used to send emails, it uses port 25.