====== steam game server ports ======
===== source dedicated server =====
The ports SRCDS officially requires are:
27015 TCP/UDP (game transmission, pings and RCON) Can be changed using -port on startup
27020 UDP (SourceTV transmission) Can be changed using +tv_port on startup
27005 UDP (Client Port) Can be changed using -clientport on startup
26900 UDP (Steam Port, outgoing) Can be changed using -sport on startup
SRCDS has also been spotted opening connections on 27005 and 51840 UDP, but these may be outbound only.
https://developer.valvesoftware.com/wiki/Source_Dedicated_Server
sudo ufw allow 27015/tcp
sudo ufw allow 27015/udp
sudo ufw allow 27020/udp