[-Sky]

i had encountered a error. i can connect to my server using my own computer by typing "connect 218.212.7.39" but unfortunately, my friends tried entering, they've got error stating that unable to connect because failed after 10 tries.
i did open the port that explains why game tracker can detect that my server is online and not offline.
is it because i'm on router? cos wad i saw was private address (192.168.1.1) instead of my public address. (218.212.7.39)

(i did port forward - that explains why game tracker found my server and it's showing online)

[ColdnessCalms]

sv_allow_lobby_connect_only 0
^This might be useful if your friends are trying to connect to IP rather than lobby

sv_lan 0
^I'm sure you knew this one already as well :S

Other than that I'm not quite sure. It is most likely a problem with your connection (I know I know, your ports are forwarded, but double check those and see if anything else is needed for your kind of connection. ***CONSIDER contacting provider)

[MjrNuT]

Are you hosting on the same PC that you are playing on? If so, that is highly not recommended. I know some ppl have gotten it to work, but it is rare.

Since you are hosting the server and just in case you have 2 different PCs (1 server and 1 you play), and your ports are forwarded correctly, then the server for L4D should be set to port a port NOT 27015. Pick 27016 instead.

So make sure though, 27015 and 27016 are still forwarded to that server.

Maybe this will help sort your problem.