I want to develop one PPPoe-like server, so I can create a virtual connecting among server and client. Is there any opensource project for reference ？ Thanks
pppd can do PPPoE (and about a billion other things). I'm not sure what you mean by "virtual" though. Both ends of PPPoE connection have to be on the same Ethernet LAN (strictly speaking there are ways around this, but that involves solving the same problem I think you are trying to solve).
I think you may be more interested in a VPN (Virtual Private Network).