Minecraft server only works from my laptop, but not from my PC (ports are forwarded and other servers work)

[/u/Natural_Research_865]

Hi everyone, I’m completely stuck with a weird networking issue.

I’m trying to run a Minecraft server, but it only works when I host it from my laptop. When I run it from my main PC, it’s not accessible from the internet at all.

Here’s the situation:

I asked my ISP to forward these ports to my PC:
27757, 26656, 25575, 8080

Previously, when the server was on my laptop, they forwarded:
25565, 25566, 25567 — and everything worked perfectly.

Now the problem:

• If I run the server on my laptop, people can connect using my public IP.
• If I run the server on my PC (not at the same time), even I can’t connect using the public IP.
• Locally (LAN) everything works fine.
• I’m currently using port 26656, but I tried all the others too.

Plot twist:
If I run a simple Python HTTP server on the same ports, people can access it from the internet. So port forwarding clearly works.

But Minecraft server? Completely unreachable from outside.

What I already tried:

• Windows Firewall rules (allowing Java and the ports)
• Disabling firewall entirely (for testing)
• Reinstalling Java
• Different server cores (Paper, Purpur, Vanilla)
• Double-checking server properties
• Different ports

Still nothing.

So:

• Same network
• Same router
• Same public IP
• Same forwarded ports
• But only the laptop works, PC doesn’t.

At this point I have no idea what else to check.
Could this be some Windows-specific networking issue or ISP-level filtering for Java/Minecraft traffic?

submitted by /u/Natural_Research_865
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