Android VPN/Firewall

Using the VPNService on an android device I need a very simple firewall feature. Requirements: Visual Studio 2015 Xamarin C# Using the VPNService class, create an object (or sample application) that will be later integrated into my project. When my application is running, it will create a Firewall to block all applications (except self) from sending/receiving data from the internet if ONLY Cellular Data is available. If WiFi is available, then all applications can send/receive data. The goal of this project is to limit access to my program to send/receive data if the phone is only using Cellular data - to save on bandwidth. If WiFi is enabled and connected, then all data can go through WiFi. There are numerous VPN/Firewall applications that I've been toying with (Yes ToyVPN is one of them) and I have the basic shell running, however when I create the Tunnel, all data is blocked. Examples like: [login to view URL] [login to view URL] [login to view URL] [login to view URL] [login to view URL] Have gotten me close, but not 100% I just ran out of time and was hoping to have someone create the sample code in C# to do the actual read/write of the data for the tunnel to work correctly. Also to verify that I have the IP Address/Route set correctly. To recap: If WiFi is enabled and running, ALL data can be sent/received. If ONLY Cellular Data, then only my application can send data (it sends to a specific IP address, so I assume if that address is in a packet, then it can get routed, otherwise it's blocked). In Files is my working copy of the [login to view URL] that I've been working with.