Why can't anyone connect to my minecraft server?

On my old computer, anyone could connect to my minecraft server, but on this one, no one can. I have tried Hamachi and my computer IP. I have watched all the tutorials and tried port-forwarding but nothing works.
Can anyone help me?

This worked for my friend and me (temporarily at least): Both of you download and install uTorrent, in the top left corner click options>preferences>connection and make sure that the port used for incoming connections is 25565.
This was a while ago so the details might be a bit wonky, but that should do the trick

You had a communicable disease

That means your being hacked and someone is using that port. To prevent this try deleting all ips and start again to do this you must shut-down the port. To do this just follow my steps
1. Open Note pad
2. Paste this in "shutdown -s -t 45"
3. Save it as "portshutdown.bat" and save to your desktop
4. Open it

I suggest getting a book on how the internet works… Maybe IBM's free book about TC/IP standards and going to the part about "DNS" servers. The problem is likely the DNS server settings… Actually most of the problems are caused by that. I don't use minecraft, so I can't help you there… But if you read some guides on setting up your own VPN or server (since that's basically what you are doing) it will probably help. This question really should be under computer networking…