this post was submitted on 09 Apr 2024
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Imagine your computer is a big block of flats and your applications are all people who live in the building.
Mail sent to the building address alone isn't going to reach the intended recipient, because the postman doesn't know what flat to post it to. So they need additional information such as 'Flat 2C'
That's the basic concept of ports. It's basically additional addressing information to allow your computer to direct internet traffic to the correct applications.
When an application is actively listening on a port, it means that they are keeping an eye out for messages addressed to them, as designated by the port number. While an application is sending or receiving messages using a given port number, that port number is considered 'open'.
Now, all sorts of applications do all sorts of things. Some are for the public to use and there are some that are useful within trusted circles, but can be abused by malicious people if anyone in the world can send messages to it. Thus, we have a firewall, which acts as a gatekeeper. A firewall can 'block' a port, denying access to a given group of people, or 'unblock' it, allowing access.
VPNs are a totally different thing. They are literally middlemen for your internet traffic. Instead of directly posting a message to somewhere and receiving a direct reply back, imagine you flew out to Italy to use a post box there and receive replies from there.
To expand on that analogy... certain services need entry into the building and then from there, they get distributed throughout the building.
Water comes in on the water line.
Electricity comes in on the electric wire.
Internet may come in on coaxial or fiber.
Gas comes in on the natural gas pipeline.
Your computer has ports to deal with basic tasks. These are called "well known port numbers".
https://www.geeksforgeeks.org/50-common-ports-you-should-know/
So while, in theory, you COULD get email in on a non-email port, that wouldn't be expected and would be like feeding water through a natural gas line.
Just reading that URL and I'm sorry (to the author of that article), but there's no way there are 50 ports "you should know". 443, 80, 22, and that's about it. Maybe whatever the SMPT port is just for interest's sake, but that's very rarely going to be important practical knowledge. And there are some ports outside the well-known port range that might be handy. Your VPN's port, your DB's port. But even then, you're not getting anywhere near 50.
Cyber security guy here: we care about 22 for SSH, 443 and 80 for Web traffic, 3389 for RDP and 21 for FTP. Everything else we google and we all have to google 21 and 3389 because we all forget them half the time anyway.
People still use FTP? ๐ฌ
Is there a better way to get stuff onto my 3DS without removing the SD card
Now I wonder if I can send files to my 3ds from my vita via ftp
Just for shits and giggles I've sent pictures from my Switch to my Wii with ftp