VPN/Proxy service hosting: HTTPS/SOCKS5 over NAT, is it realistic?

Question

VPN

There is a machine sitting behind NAT'om.
Question:
Can I host a VPN or PROXY service on it? What are NAT bypasses?
And can it be done through Teredo?
Without the participation of IPv6 issuing services (in the world).

Answer 1

Found a solution in a software called JabPunch using p2p reception:
Connection:
PC #1 -> Stun Server -> infa konnnekta PC#1 -> Stun Server -> PC #2
PC #2 -> Stun Server -> infa konnekta PC # 2 -> Stun Server -> PC #1
OpenVPN is built into the software, as well as remote access (nt 6.0/6.1) and a couple of other small functions.
But strangely, I raised the web server, everything responded successfully to port 80, but it was silent on the http (default 3128) proxy ...