IP Addresses, DNS & Ports, Explained

The address book of the internet: what an IP address really is, how DNS turns names like example.com into numbers, and how ports let one machine run many services at once.

1. IP Addresses - A Machine's Number An IP address is the number that identifies one machine on a network; IPv4 ran out of numbers so IPv6 added far more, and your home devices share a single public IP while each keeps a private one.
2. DNS - Names to Numbers DNS is the internet's phone book: typing example.com triggers a lookup that returns an IP address, handled by a chain of resolvers and sped up by caching - and when it breaks, sites feel down even when they aren't.
3. Ports - One Machine, Many Doors A single machine runs many services at once, each behind a numbered port; the real address of a service is the IP plus the port, and common ports (80/443 web, 22 SSH) tell you what's listening where.