This project consists of three Python scripts that implement a basic VPN (Virtual Private Network). The VPN is created using a TUN interface, a network layer device that operates on layer 3 packets like IP packets. TUN interfaces are software loopback mechanisms that can be controlled by user-space programs.

1. ToyVPN.py: This script can function as both a VPN server and a client. It can establish a VPN connection with a remote server or listen for incoming connections as a server. The script includes functions for encoding and decoding data using Base64. I tried to bypass the GFW using this technique, but my server quickly got banned for transferring big amount of data.

2. ServerVPN.py: This script is the server-side component of the VPN. It listens for incoming VPN connections, authenticates clients, and maintains the VPN sessions.

3. ClientVPN.py: This script is the client-side component. It is used to establish a VPN connection with the server. It sends a keepalive message to the server every few seconds to maintain the connection.

To use these scripts, you need to run them with specific command-line arguments.

For the ToyVPN.py script, run:

sudo python3 ToyVPN.py client [remote_ip] [remote_port]

Or

sudo python3 ToyVPN.py server

For the ServerVPN.py script, just run:

sudo python3 ServerVPN.py

This script doesn't require any command-line arguments. It will start a VPN server that listens for incoming connections.

For the ClientVPN.py script, run:

sudo python3 ClientVPN.py [remote_ip] [remote_port]

The [remote_ip] and [remote_port] arguments specify the VPN server's IP address and port.

The scripts use a password for authentication, which is defined as PASSWORD in the scripts. It's currently set to b'4fb88ca224e'. If you want to use a different password, you need to change this value in all three scripts.

The VPN network is defined by the NETWORK variable in the scripts, which is currently set to '10.0.0.0/24'. The IPRANGE variable is a list of the IP addresses in this network.

The server binds to the IP address and port specified by BIND_ADDRESS, which is currently set to '0.0.0.0',2003. This means that it listens on all available network interfaces and port 2003.

These scripts are basic implementations of a VPN and are likely not suitable for use in a production environment. They do not include many features that a full-featured VPN would have, such as encryption, compression, or support for multiple concurrent connections. However, they can serve as a starting point for learning about VPNs and network programming in Python.