All data transmitted over the internet is sent and received using a specific set of commands, also known as a protocol. Each protocol is assigned a specific port number. For example, all website data transferred over HTTP uses port 80. Data sent over HTTPS uses port 443. Other common ports include:

Port 20 - FTP (file transfer protocol)

Port 22 - SSH and SFTP

Port 25 - SMTP (outgoing email)

Port 465 - SMTP over SSL

Port 143 - IMAP (incoming email)

Port 993 - IMAP over SSL

Port numbers are similar to wireless channels in that they prevent conflicts between different protocols. They also provide a simple way to implement network security measures, since it is possible to allow or block specific protocols.