Which ports
Players only need the server's game port, over UDP. HaruHost picks it from your port range (33000–33100 unless you change it), so two servers never clash, and shows it on the Details tab, under Advanced → Ports In Use. The ports HaruHost uses to talk to the server stay private and need no forwarding.
Forward once for every server
Because every server's ports come from the same range, one forwarding rule for the range covers every server you will run on that PC. Settings → Network shows the rule to add (your PC's address, the range and the protocol), a link to your router's page and a diagram.
Let HaruHost open the ports
With Auto-manage UPnP on, HaruHost opens the server's ports on your router every time it starts and removes old rules. Each server's network page shows whether its ports are open, missing or pointing at another PC, and Settings → Network lists every rule HaruHost made.
Windows Firewall
With Auto-manage Firewall on, HaruHost adds the firewall rules when the server starts. The firewall check finds missing rules and a network set to Public, and Fix repairs them.
On a VPS
On Linux, open the port range in your provider's firewall. HaruHost already gives every server its port from that range. See Palworld on Linux.
The router and firewall helpers are on Windows. If your internet has no public address, use the Tunnel instead.
Questions
What port does a Palworld server use?
8211 over UDP by default. With HaruHost, each server gets its own game port from your port range, shown on its Details tab.
Can I run two Palworld servers behind one router?
Yes. Each server gets its own port from the range, and one forwarding rule covers them all.