Server Not Responding?

Hello Mac here.

I have just set up a server using the valve server tool. I have opened the 27015 port on my modem and i can connect to my server. Before i opened the 27015 port on my modem i couldn’t connect but after opening the 27015 port my friend trys to join it says “Server Not Responding”.

So please could some one give me a solution?

Give your WAN IP out to your friends (your internet ip) If you are unable to find it yourself use something like http://ipchicken.com. If your connecting to the server locally they wont be able to join because steam will try to connect them to 192.168.x.x which is a local ip only you could access behind your modem/router.
If it still does not work check to make sure the port is correctly opened and you are allowing the server through any firewalls on your computer.

Did you type the commands into the console from within the server to make it appear on the list so others can join.