Your IP address gets packets to your computer. But which application should receive them? Ports are how your computer runs dozens of network conversations simultaneously without mixing them up.
IP addresses find computers. Ports find the services running on them. Together they create sockets—the addressing system that lets one machine do a thousand things at once.
A 1970s decision to use sixteen bits for port numbers created a permanent constraint on every networked device. Here's why exactly 65,536 ports exist, what the three ranges mean, and why some require root.
The first 1024 ports are reserved for the Internet's essential services—HTTP, SSH, DNS, email. Here's why port 80 means web traffic everywhere on Earth, and what happens when you try to claim these ports for yourself.
The 48,127 ports between privileged services and temporary connections run on something stranger than enforcement: collective agreement. How MySQL, PostgreSQL, and Redis claimed their territory—and why one port number honors an Italian TV actress.
Your computer assigns temporary port numbers for every outgoing connection—a return address for each conversation. Here's how ephemeral ports work and what happens when you run out.
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