Dedicated Server fails all P2P connections on Windows Server 2025 (Peer2Peer_ConnectionFailed Timeou

Hello,

I am experiencing a critical issue where no players can connect to my Space Engineers Dedicated Server. Every connection attempt times out with this message in the server log:

Peer2Peer_SessionRequest Peer2Peer_ConnectionFailed Timeout

This happens 100% of the time and the server is completely unreachable.

But the server is visable and pingable in the server browser...

Below is the log excerpt:

2025-12-03 11:18:21.790: Peer2Peer_SessionRequest [xxx] 2025-12-03 11:18:36.786: Peer2Peer_ConnectionFailed [xxx], Timeout

Full server startup log (relevant parts):

App Version: 01_208_015 Networking service: Steam Server connected to Steam Public IP: 82.xxx.xxx.xxx Server Name: The Survivalists World Name: Alien Planet Game ready... Plugin Init: MultigridProjectorDedicated.MultigridProjectorPlugin Peer2Peer_SessionRequest Peer2Peer_ConnectionFailed Timeout

The server never reaches “GameServer Logged On” in the logs, which normally appears when SteamNetworking initializes correctly.

• OS: Windows Server 2025 Standard
• CPU: Ryzen 9 9900X
• Steam logged in and running
• Space Engineers Dedicated Server installed via Steam
• No NAT (dedicated host, public IPv4)
• Ports open: 27015 / 27016 / 8766 / 27000–27050
• DDoS filtering disabled for testing
• Windows Firewall on/off tested
• Fresh world created
• Tested with and without mods
• Tested with and without plugins
• Clean reinstall of the Dedicated Server

• Fully disabled Windows Firewall
• Fully allowed all SE and SteamNetworking ports
• Verified external port accessibility
• Disabled DDoS filtering
• Tried different game ports (27016, 29016, etc)
• Reinstalled the entire Dedicated Server
• Tested fresh empty world
• Tested vanilla (no mods)
• Tested plugins disabled
• Restarted Steam and OS multiple times
• IPv6 on and off tested
• Verified that Steam reports “Server connected to Steam”

None of these changed the behavior.

All clients still get stuck at “Connecting…” and eventually time out.

I also want to mention that I host other game servers on the same machine without any issues, Arma, DayZ, Valheim, Farming Sim 25 etc. etc.

<div><div><div></div></div><div><code>Peer2Peer_ConnectionFailed Timeout
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