I've solved this issue. If anyone has this same problem, that's how i've fixed it:
Go to your antivirus and then, in firewall settings, allow the "javaw.exe" (at C:\Program Files (x86)\Minecraft\runtime\jre-x64\1.8.0_25\bin) for trusted programs.
- "jre-x64" Probably depends of your system.
- "1.8.0_25" The same of above, don't have to be exactly that name.
Hope this helps!