Port forwarding for a Icarus server
Icarus uses two UDP ports: 17777 for the game and 27015 for the Steam query. Both are set with launch arguments, -PORT= and -QueryPort=, and both need forwarding.
Your setup
Choose the firmware family rather than your exact model — every router in a family shares the same menus.
Out of the box it is 17777. If you changed that, use whatever you set in -PORT= launch argument.
The local address of the computer that runs the server. Find it with ipconfig on Windows or ip addr on Linux; it will begin with 192.168, 10. or 172.
Open these
Your firmware takes ranges, so each line here is one rule.
- 17777 UDP
- 27015 UDP
17777UDPGame trafficPlayers connect here over UDP.27015UDPSteam querySet with -QueryPort=. Needed for the server browser.
Do not open these
Good news: this game has no remote-admin port that could be exposed by mistake. Forward the ports on the left and stop there.
Step by step: your router
- 1
Give the server a fixed local IP
A forwarding rule targets a single local address. If the server comes back from a reboot with a new one, the rule quietly points at an empty address — which is how forwards seem to "break by themselves".
On this router:look for DHCP Reservation, Address Reservation, Static Lease or Manually Assigned IP
- 2
Open the router admin page
From a device on the same network, open one of these in a browser:
- 192.168.0.1
- 192.168.1.1
- 192.168.2.1
- 10.0.0.1
Almost always printed on a sticker on the router itself.
- 3
Find the port forwarding page
Port Forwarding, Virtual Server, NAT, Applications & Gaming, or Port Mapping
Vendors use at least six names for the same feature. Whatever it is called, the page you want is the one asking for a port, a protocol and a device on your network. If the external and internal port fields both exist, set them to the same number.
- 4
Create one rule per line
a description field, if there is one External / WAN / Public / Service port Internal / LAN / Private port Protocol Internal IP / Device / Server IP Icarus 17777 17777 UDP your server’s local IP Icarus 27015 27015 UDP your server’s local IP Use the same number for the external and internal port. You can make the external one different, but then every player has to connect on that new number, so keep them identical unless you have a specific reason not to.
- 5
Let the server through its own firewall
The router is now sending traffic to the right computer, but that computer can still turn it away. Windows Defender Firewall is the usual offender: it blocks a newly installed dedicated server by default, and from outside that is indistinguishable from a broken forward.
Take it with you
Icarus — port forwarding rules ------------------------------ 17777 UDP -> <server local IP> 27015 UDP -> <server local IP>
Check whether it worked
Always test from outside your network. A connection from another device in the house proves nothing: that traffic stays on your LAN and never passes through the rule you just created.
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The usual mistake
Changing -PORT= and forgetting -QueryPort= is the usual mistake when running two servers on one machine — the second server takes the same query port as the first and never appears in the browser. Give each server its own pair.
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Skipping port forwarding
A hosted server keeps a persistent prospect running between sessions without a home PC left on, which matters most for Open World prospects that are meant to continue for weeks.