Q: What open ports my firewall needs for steam to work? (#6)

A: If you use a router these ports must be open in order for steam to work correctly.
Computers running Dedicated Servers need these ports open:
UDP: 27015 and 27020 (default HLDS port)

For software firewalls, no ports have to be opened, just add hl.exe and steam.exe to the program list on your firewall. It will open the proper ports at the executables request.

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