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Steam.exe (main exception): unable to load library Steam.dll

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[email protected]

Inactive Moderator
Sep 27, 2003


I received this error while trying to install Steam and was able to successfully diagnose the issue. For me it was a firewall issue. I had downtime today and decided to install Steam onto my laptop while somewhere other than home, and was getting the error that you see in the title:
Steam.exe (main exception): unable to load library Steam.dll

I believe software firewall can cause this, but my software firewall (Trend Micro) prompts me for everything on the fly, which I just say "add" or something similar.


The issue was the firewall. The firewall I was behind during the issue was Astaro. Fortunately, I have access to the firewall and here are the ports that I opened:
TCP 27015-27050
UDP 27000-27015
UDP 1200

I'm not sure which of these was the fix, but it's too late now as I got passed the error and don't feel like replicating it in order to find out the EXACT port(s)/protocol(s) necessary. If anyone wants to add info to this thread, please feel free. Try TCP 27020-27029, then 27030-27039, and so on, until the problem is fixed; if not, try the UDP ports one by one. I'm curious as to what was the EXACT fix.

For those that are browsing on the net, the solution isn't always the easiest - which I've read to be to download the DLL file and copy it to your steam folder. Sometimes it's deeper than that. You need to do a full diagnosis of what is BLOCKING (hardware or software firewall(s)) the Steam install from accessing Steam's database(s) for retrieving whatever data it needs (particularly the DLL file in this case).

I hope this helps those in need. I just wanted to publish this for the good of someone's potential future problem. It took me about 90 minutes to figure out the problem, but it would have taken me less time if I had worked with Astaro firewall before - most of the time I was trying to figure out HOW port forwarding works on the hardware firewall as I haven't used Astaro before.

Most people will be behind a simple router, so just go to your PORT FORWARDING section and open the ports I listed above in YELLOW BOLD... or send me a PM or email through this forum.
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