Quote fromWith the current client, you cannot connect to servers if you aren't connected to the internet.
If your server is running, and your client has internet, try this:
Go to this url: www.minecraft.net/play.jsp?ip=[server-ip]&port=[server-port]
replace [server-ip] and [server-port] with the appropriate ip/port
I tried this but it failed
EDIT: NVM Fixed I didnt got the url correct. I did instead of IP= server=
then it kinda fails...