These settings are listed on Valve's site in the help section, enable these ports on your router (if you have one). I've been using these for a couple years now and it's been great.
UDP 27000 to 27015 inclusive (Game client traffic)
UDP 27015 to 27030 inclusive (Typically Matchmaking and HLTV)
TCP 27014 to 27050 inclusive (Steam downloads)
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)
Go to Start > Run and type in: regedit.
Navigate to: HKEY_CURRENT_USER\Software\Valve\Steam\.
Create a new string value registry setting named CafeRate.
Give the CafeRate regkey a value of 10000 and progressively decrease the value until the issue is resolved. A rate of 3000 should be considered the minimum value.
The above also helped with the 'no servers' issue on my network. I guess on some setups the server listings end up looking like flood traffic so the list will lock up on you :/ (frustrating lol). This registry value will lower that rate that the list populates at.
I hope that helps a little, have fun in TF2. Maybe I'll see you there sometime. :3
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