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Can someone demystify computer Ports for me? Please? Blocking, unblocking, opening, allowing, VPNs and their effect, what ports are and what they do, step by step, when you have to interact with them? (lemmy.dbzer0.com)

submitted 8 months ago by [email protected] to c/[email protected]

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It's the one thing when I'm configuring things that makes me wince because I know it will give me the business, and I know it shouldn't, but it does, every time. I have no real idea what I'm doing, what it is, how it works, so of course I'm blindly following instructions like a monkey at a typewriter.

Please guide me into enlightenment.

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[–] [email protected] 3 points 8 months ago* (last edited 8 months ago) (1 children)

This is really good, I just want to clarify one thing:

there are specific protocols that are traditionally used on those specific ports

Protocols are not 'used on ports', it's actually the other way around: TCP and UDP are both protocols operating on top of IP, each with its own set of ports to help direct traffic, exactly as you explained.

There are other protocols, like ICMP or GRE, that exist quite happily without knowing anything about ports (ICMP has types and codes, GRE doesn't).

Edit: I suppose it is actually a bit ambiguous because we also refer to applications (HTTPS, telnet) as protocols. I'm not sure if there is a standard way to differentiate when discussing other than just saying transport layer protocol / application layer protocol.

[–] [email protected] 2 points 8 months ago

Yeah, didn't want to dig deep in the interest of brevity, but I didn't want to say that specific applications use those ports, even though I already said that ports in general are for applications. You can use whatever ftp, ssh, or http server you want as long as they "speak" the expected protocol.