I want to use my primary internet connection (eth0) on my PC for all traffic, but route traffic over a pptp VPN for specified application/or port.
Details
eth0 = current internet port
pptp1 = VPN connection which ha its own public IP address accessible from the internet.
The connection I want to route out of the pptp1 interface is in response to an incoming connection.
Incoming port will be always: 33340 Outgoing port can be change, but usually it is 33330