Ports
In depthConcept
Also known as: Poorten, Netwerkpoorten
Numbers (0 to 65535) that decide which application on a machine receives the network traffic.
Ports, explained
Written by EduVerseWhat it is
A port is a number that, together with an IP address, says which program on a machine should receive incoming traffic. One server can run a web server, a database and SSH side by side because each listens on its own port. Many services have a conventional number, like 443 for HTTPS.
Why teams use it
Without ports, a machine would have no way to know which application a packet is meant for. Ports also show up in firewall rules, Docker port mappings and connection strings, so many “it won’t connect” problems turn out to be the wrong port or a port that isn’t open.
An example from work
You start your Express server with node server.js and get “EADDRINUSE: address already in use :::3000”. A server you started earlier is still listening on port 3000. You stop that process, or start the new one on a different port, and the app loads again.
Our own explanation, not a quote from the book.
In the book
Sentences from The Software Realm, Decoded that mention Ports, exactly as printed.
4 more passages about Ports in the full book
Read every conversation where Ports comes up, with the interactive slides and demos.
Where it fits
Routing network traffic to the right application
Coverage in the book
Covered in depth: multiple pages with explanations, examples and simulations.
