From their Website
Team Fortress 2 Classic is a re-imagining of the 2008-2009 era of the original Team Fortress 2, of which is what we consider the "Classic Era", featuring old features that were scrapped and worked upon, or new content such as new weapons and gamemodes.
TF2C servers require 1 port to be open, the SourceTV port can also be opened for spectators.
| Port | default |
|---|---|
| Game/rcon | 27015 |
| SourceTV | 27020 |