Left 4 Dead 2 ports?

Kooter · **Author**

Hi, I'm trying to tighten up my ports on my firewall to help lessen Dos attacks and I've found this guide https://forums.alliedmods.net/showthread.php?t=189327 which indicates I can pretty much block off all but UDP ports 27015 and 27020. It also says I can block off I can block off ICMP unless I want to ping my server. I've tried tons of combinations but almost all port blocking that I've done says my server is disconnected from Steam when I block them. I've opened ports 27000-27050, 4380 and 51840. I've collected this information from https://forums.alliedmods.net/showthread.php?t=189327, https://developer.valvesoftware.com/...dicated_Server and here http://portforward.com/cports.htm.

From what I've read, L4D2 only uses TDP protocol for rcon and TCP can be blocked entirely. I've also tried not blocking any TDP ports but still get the same problem. From what I can tell the problem lies with the UDP protocol. I've unblocked every protocol but UDP. I've opened UDP ports 4380, 27000-27050 and 51840, which still seems to give me the message in console about the server no longer being connected to Steam. I'm trying to harden my server against Dos attacks a little better. When the message about the server not being connected to Steam occurs, the server will show up in my group servers list, but game info will not show. Can anyone tell me what UDP ports are needed to be open for L4D2? Thanks.

Ellie · 06-12-2014 , 13:17 Re: Left 4 Dead 2 ports?

The l4d games don't need port 51840. This server is in your house or what? Their is also this Metamod source plugin you can try:

https://forums.alliedmods.net/showthread.php?t=95312

Geek_Loco · 06-12-2014 , 13:33 Re: Left 4 Dead 2 ports?

I have helped several clans run local Source servers, including The Ship, CS:S, CS:GO, L4D, L4D2, TF2, HL2

M, & NMRiH, but have never opened ports 4380 or 51840.

Ensure that the local firewall for the OS or add-on software firewall and hardware firewall (router) match ports and that the router is forwarding to the correct internal IP.

I can't think of anything else. Hope you get it resolved and post your answer to help others down the road.