C#实现UDP打洞的示例代码

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客户端
        udpClient = new UdpClient();
        udpSocket = udpClient.Client;
 
        // 获取本地端口
        int localPort = ((IPEndPoint)udpSocket.LocalEndPoint).Port;
 
        // 向STUN服务器发送请求并接收响应以获取公网地址
        byte[] request = new byte[12];
        // 填充请求数据...
        byte[] response = SendAndReceive(stunServer, request);
 
        // 解析STUN响应以获得公网地址和端口
        // 此处省略解析过程，实际项目中需要根据STUN协议解析响应
 
        // 假设我们已经得到了自己的公网地址和端口：remoteEP
        IPEndPoint remoteEP = new IPEndPoint(publicIpAddress, publicPort);
 
        // 与对端进行通信前，双方都需要通过某种方式（例如信令服务器）交换彼此的公网信息
 
        // 当收到对方的公网地址和端口后
        IPEndPoint peerEP = ...; // 对端的公网地址和端口
 
        // 尝试发送UDP数据包“打洞”
        byte[] punchData = Encoding.UTF8.GetBytes("Hello from NAT!");
        udpClient.Send(punchData, punchData.Length, peerEP);
 
        // 接收对端发来的数据，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);
    }
}