connection setting to open your NAT

[brownies]

Your network must be configured to allow Steam access to the following ports (in order from highest to lowest priority for QoS users):

Steam Client
UDP 27000 to 27015 inclusive (Game client traffic)
UDP 27015 to 27030 inclusive (Typically Matchmaking and HLTV)
TCP 27014 to 27050 inclusive (Steam downloads)
UDP 4380

Additional Ports for Call of Duty: Modern Warfare 2 Multiplayer

Application: CODMW2 External port: 1500 Internal port: 1500 Protocol: UDP

Application: CODMW2A External port: 3005 Internal port: 3005 Protocol: UDP

Application: CODMW2B External port: 3101 Internal port: 3101 Protocol: UDP

Application: CODMW2C External port: 28960 Internal port: 28960 Protocol: UDP

Application: CODMW2D External port: 27015 Internal port: 27015 Protocol: TCP

also enable upnp in your router settings and turn off background programs.

Dedicated or Listen Servers

* TCP 27015 (SRCDS Rcon port)


Steamworks P2P Networking and Steam Voice Chat

* UDP 3478 (Outbound)
* UDP 4379 (Outbound)
* UDP 4380 (Outbound)