using System;
using System.Net;
using System.Net.Sockets;
 
public class UdpHolePunchingExample
{
    private static readonly IPEndPoint stunServer = new IPEndPoint(IPAddress.Parse("stun.example.com"), 3478);
    private static UdpClient udpClient;
    private static Socket udpSocket;
 
    public static void Main()
    {
        // 初始化UDP客戶端
        udpClient = new UdpClient();
        udpSocket = udpClient.Client;
 
        // 獲取本地端口
        int localPort = ((IPEndPoint)udpSocket.LocalEndPoint).Port;
 
        // 向STUN服務(wù)器發(fā)送請(qǐng)求并接收響應(yīng)以獲取公網(wǎng)地址
        byte[] request = new byte[12];
        // 填充請(qǐng)求數(shù)據(jù)...
        byte[] response = SendAndReceive(stunServer, request);
 
        // 解析STUN響應(yīng)以獲得公網(wǎng)地址和端口
        // 此處省略解析過(guò)程，實(shí)際項(xiàng)目中需要根據(jù)STUN協(xié)議解析響應(yīng)
 
        // 假設(shè)我們已經(jīng)得到了自己的公網(wǎng)地址和端口：remoteEP
        IPEndPoint remoteEP = new IPEndPoint(publicIpAddress, publicPort);
 
        // 與對(duì)端進(jìn)行通信前，雙方都需要通過(guò)某種方式（例如信令服務(wù)器）交換彼此的公網(wǎng)信息
 
        // 當(dāng)收到對(duì)方的公網(wǎng)地址和端口后
        IPEndPoint peerEP = ...; // 對(duì)端的公網(wǎng)地址和端口
 
        // 嘗試發(fā)送UDP數(shù)據(jù)包“打洞”
        byte[] punchData = Encoding.UTF8.GetBytes("Hello from NAT!");
        udpClient.Send(punchData, punchData.Length, peerEP);
 
        // 接收對(duì)端發(fā)來(lái)的數(shù)據(jù)，完成打洞
        while (true)
        {
            byte[] receivedBytes = udpClient.Receive(ref peerEP);
            Console.WriteLine($"Received: {Encoding.UTF8.GetString(receivedBytes)} from {peerEP.Address}:{peerEP.Port}");
        }
    }
 
    private static byte[] SendAndReceive(IPEndPoint server, byte[] data)
    {
        udpClient.Send(data, data.Length, server);
        return udpClient.Receive(ref server);
    }
}