FYI I can connect fine to the server now, the port still shows "closed" on the Port Tester that you linked. /shurg

Well, I figured out the issue...

User error. /facepalm

Turns out I had a port range that conflicted with Factorio's default port pointed to another internal IP.

That being said, no clue why the known working port did not resolve the issue.

Okay, I've also tried doing a full reinstall of Factorio on the server. I've changed the port number to a known working port. I've added the server to the DMZ. None of these things have resulted in a connectable server.

Thank you for the response.

The Client and Server are 2 separate computers.

According to the external tool, the port is "closed". That being said, I checked the port on a known working server and it also appeared "closed" to the tool. So I assume the software doesn't respond to the port probe?

I've setup a headless dedicated server on my home server running version 12.24. I'm running the server with the command "Factorio.exe --start-server save1.zip" and I am able to connect over LAN.

The problem exists while trying to connect VIA WAN. I have port forwarded the port.
http://i.imgur.com ...