What kind of protocol is used in android ToyVPN?

In respect of ToyVPN (a sample client/server VPN for android), as far as i know it has no strong authentication and encryption like L2TP,PPTP, ... So,

1- What kind of protocol is used in ToyVPN?
2- Is it safe? I mean can somebody hack into the VPN tunnel?
3- if not safe; so what can i do to encrypt the tunnel?
4- Are the routers able to detect that this is a VPN tunnel? or is detected as a simple socket link?