Redirects.

If you try to connect to hypixel.net via port 443, it redirects you to the html page.

If you try to connect to play.hypixel.net via port 25565, it redirects you to the minecraft server.

The amount of confidently incorrect responses is exactly what one could expect from Lemmy.

First: TCP and UDP can listen on the same port, DNS is a great example of such. You’d generally need it to be part of the same process as ports are generally bound to the same process, but more on this later.

Second: Minecraft and website are both using TCP. TCP is part of layer 4, transport; whereas HTTP(S) / Minecraft are part of layer 7, application. If you really want to, you could cram HTTP(S) over UDP (technically, QUIC/HTTP3 does this), and if you absolutely want to, with updates to the protocol itself, and some server client edits you can cram Minecraft over UDP, too. People need to brush up on their OSI layers before making bold claims.

Third: The web server and the Minecraft server are not running on the same machine. For something that scale, both services are served from a cluster focused only on what they’re serving.

Finally: Hypixel use reverse proxy to sit between the user and their actual server. Specifically, they are most likely using Cloudflare Spectrum to proxy their traffic. User request reaches a point of presence, a reverse proxy service is listening on the applicable ports (443/25565) + protocol (HTTPS/Minecraft), and then depending on traffic type, and rules, the request gets routed to the actual server behind the scenes. There are speculations of them no longer using Cloudflare, but I don’t believe this is the case. If you dig their mc.hypixel.net domain, you get a bunch of direct assigned IP addresses, but if you tried to trace it from multiple locations, you’d all end up going through Cloudflare infrastructure. It is highly likely that they’re still leaning on Cloudflare for this service, with a BYOIP arrangement to reduce risk of DDOS addressed towards them overflow to other customers.

In no uncertain terms:

1. Hypixel.net has Cloudflare DNS for their domain.
2. For their website, it has orange cloud enabled to proxy traffic through CF’s global CDN and DDOS protection service.
3. For their Minecraft server, they advertise mc.hypixel.net, but also have a SRV record for _minecraft._tcp.hypixel.net set for 25565 on mc.hypixel.net
4. The mc.hypixel.net domain has CNAME record for mt.mc.production.hypixel.io. which is flattened to a bunch of their own direct assigned IP addresses.
5. Traceroute towards those direct assigned IP addresses goes through Cloudflare infrastructure but final destination is obscured, just like their website, to protect them from DDOS attacks.

Minecraft can read a special DNS record type called SRV records. You can create a record like that to point Minecraft to a port that the server is running on. It doesn't even have to have the same ip as the webserver.

This is for Namecheap, but the general principle applies everywhere: https://www.namecheap.com/support/knowledgebase/article.aspx/9765/2208/how-can-i-link-my-domain-name-to-a-minecraft-server/

DNS A record points to an IP destination. Ports are then handled by the requests for a specific port thing.

Example: A record for www.dududu.com points to IP 1.2.3.4, but different service ports are listening there to pick up different traffic.

Don't forget, you can also use SRV records to point a domain to another target, where you can also omit the port number. So connecting to server.org say, can point to mc.server.org:25565 under the hood.

This prolly isn't what hypixel are doing as everything's likely on the same network and their router/firewall is just forwarding traffic onto different machines, but SRV is one way to redirect a minecraft connection (and you could combine the technique with subdomains).