Bug #1554

NAT Traversal Failure Post SDK/Windows Update

Status:	Open
Priority:	High
Added by:	mitbit on May 27, '26
Assigned to:	Unassigned
Due date:
Reported for:	S06.04

Steps to Reproduce

1. Connect to a game or host your own
2. Open Steamworks Network Connections
3. Observe that there are no direct connections

Explanation

NAT traversal is broken. On the client side you get the message 'NAT traversal failed (3999)'. On the host side the error is 'NAT traversal not attempted. Remote host did not share any IP addresses'. I don't know if it was a Steam SDK update or a Windows update that broke it. ProcMon shows that the game cannot load the steamwebrtc64.dll library. Copying that file to one of the DLL Search Order folders enables NAT traversal to work properly. I tested it and it looks like everyone plays via Steam Datagram Relay servers (see the attached pic). Most players probably don't even notice it. However players in countries without relay servers experience 2-10 times higher latency.

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