Use powershell to allow a UDP IPv4 client to connect to an IPv6 host

udp46.ps1

Add-Type -TypeDefinition @"
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;

public static class UDPForward
{
    public static void Main(string[] args)
    {
        // Define the local IPv4 listening endpoint
        IPAddress localIPAddress = IPAddress.Any;
        int localPort = 27016;
        IPEndPoint localEndpoint = new IPEndPoint(localIPAddress, localPort);

        // Define the remote domain name and port
        string remoteHost = "IPv6 L4D2 Server";
        int remotePort = 27016;

        // Resolve the remote domain name to an IPv6 address
        IPAddress[] remoteIPAddresses = Dns.GetHostAddresses(remoteHost);
        IPEndPoint remoteEndpoint = new IPEndPoint(remoteIPAddresses[0], remotePort);

        // Create a UDP client socket to listen for incoming IPv4 traffic
        UdpClient udpClient = new UdpClient(localEndpoint);

        // Create a UDP client socket with IPv6 address family to send data to the IPv6 host
        UdpClient udpClientRemote = new UdpClient(remotePort, AddressFamily.InterNetworkV6);
        udpClientRemote.Connect(remoteEndpoint);

        // Start listening for incoming IPv4 traffic
        Console.WriteLine("Listening for incoming UDP IPv4 traffic on " + localEndpoint.Address + ":" + "localEndpoint.Port");

        // Start a thread for receiving IPv4 traffic and forwarding it
        Thread receiveAndForwardThread = new Thread(() =>
        {
            while (true)
            {
                // Receive data from the IPv4 client
                byte[] receivedData = udpClient.Receive(ref localEndpoint);

                // Send the received data to the resolved IPv6 address
                udpClientRemote.Send(receivedData, receivedData.Length);
            }
        });

        // Start a thread for receiving IPv6 traffic
        Thread receiveThreadRemote = new Thread(() =>
        {
            while (true)
            {
                // Receive data from the IPv6 server
                byte[] receivedDataRemote = udpClientRemote.Receive(ref remoteEndpoint);

                // Forward the received data to the local IPv4 client
                udpClient.Send(receivedDataRemote, receivedDataRemote.Length, localEndpoint);
            }
        });

        // Start both threads
        receiveAndForwardThread.Start();
        receiveThreadRemote.Start();

        // Wait for threads to finish (in this case, indefinitely)
        receiveAndForwardThread.Join();
        receiveThreadRemote.Join();
    }
}
"@

# Start the C# program
[UDPForward]::Main(@())