I can't connect to most Minecraft servers?

Make sure your properly connected to the internet, plus make sure the minecraft server you are trying to join is supported in the version you are playing.

I'm connected to the internet. Friends can connect to it. I can't. I can't host. I'm port forwarded. When I check for open ports with online tools it says that it's closed. I did it correctly. I'm very good with computers. All my friends come to me for help. I don't know what would cause this. Firewall opened, no AntiVirus.