Cannot connect to my friend's server

Title kinda says it all. I cannot connect to my friends server BUT all my other friend’s can easily! When ever I try to connect it either says “Server not responding” or “failed to connect after 4 retries” or something like that. Anyone know why this is only happening to only me and no one else?

Try opening your console and typing connect ipgoeshere.

the console thing doesnt work =( anyone else know what the problem is?

Portforward 27015 and 27005 on your friends firewall and router.

Check settings on your firewall, port forward the ports on your own router if you like too.

Can you connect to any other GMod servers?