I am trying to create a VPN server on my Windows 8.1 machine at home so I can connect to it when I am on public wifi(using an Android device). I know Windows has a built in VPN (PPTP) and I was able to set up a connection, but for some reason it stopped working a day or two after. I did not make changes on my server machine or my phone so I have no idea why it stopped working. I don't know how to even troubleshoot since the only message I get is "Unsuccessful" on my Android phone. Anyone have an idea how can troubleshoot this or can offer an alternate solution that's easy to set up?