Well-Known Ports

If a port is just a number, how does your browser know which one to use? By convention. Some numbers are agreed on by everyone:

• 22: SSH, remote shell access
• 53: DNS, the lookups from the last chapter
• 80: HTTP
• 443: HTTPS

This is why you can type an address with no port at all. http:// means port 80 unless you say otherwise, and https:// means 443. Writing http://example.com:80 is simply saying out loud what was already assumed.

They are conventions, not rules. Nothing stops a web server running on 8080, and plenty do.

There is one real restriction. Ports below 1024 normally require administrator rights to listen on, which is why development servers use numbers like 8080 or 3000: no special permission needed.