Какие порты должны быть отрыты для работы Steam?
Цитата с сайта steampowered.com: The following ports must be open in your firewall and router for Steam and Steam Games to work: UDP 27000 to 27020 inclusive
TCP 27020 to 27050 inclusive
TCP 27040 and 27041*
*CyberCafe Owners only Computers running Dedicated Servers need these ports open: UDP: 27015 and 27020 (default HLDS, SRCDS and HLTV port)
TCP: 27015 (SRCDS Rcon port) | 
