Raspberry Pi can be used as a VPN server to allow users to setup a secure tunnel from a remote client to the local network. Once a VPN tunnel is established between the Raspberry Pi and the client device, such as laptop, mobile device, ipad, itab, etc; if the port forward of router and access right is setup probably, then, the device can be accessed from local network or vice verse. I can successfully use pttpd software to setup VPN feature, and I will explain the setup step in the following.
Step 1. To make the latest update of the System:
$ sudo apt-get update