怎么在收到ICMP请求包后，回复自定义消息

liguicd 2014-02-11 12:31:19

最近在研究ICMP通信，遇到了一个比较郁闷的问题，ICMP请求可以顺利地发送到服务器的接收程序上，但是在回复时，却发现客户端老是接收不到服务器发送过来的自定义消息。大侠们帮忙看看，是否有啥解决思路和办法的。

问题：
怎样才能让客户端接收到服务器端发送过来的自定义消息"good day"，
而不是接收到客户端本身之前发出的"howdy pilgrim"？

运行环境：
client处在一个局域网内部，通过一个路由器连到外网，路由器并未作端口映射到client上。
server已经接入外网，拥有独立IP：115.115.115.1（假设）

代码：
ICMP client:



static void Main(string[] args)

    {

        Ping icmpClient = new Ping();

        PingOptions options = new PingOptions();

        options.DontFragment = true;

        byte[] msg = Encoding.UTF8.GetBytes("howdy pilgrim");



        while (true)

        {

            PingReply reply = icmpClient.Send("115.115.115.1", 60 * 1000, msg, options);

            string responseReceived = Encoding.UTF8.GetString(reply.Buffer);

            Console.WriteLine(DateTime.Now.ToString() + "    Response from server: " + responseReceived);

            Thread.Sleep(500);

        }

    }

ICMP listener:



static void Main(string[] args)

    {

        while (true)

        {

            Socket icmpListener = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);

            icmpListener.Bind(new IPEndPoint(IPAddress.Parse("192.168.1.3"), 0));

            icmpListener.IOControl(IOControlCode.ReceiveAll, new byte[] { 1, 0, 0, 0 }, null);



            byte[] buffer = new byte[1024*1024];

            EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);               



            int bytesRead = icmpListener.ReceiveFrom(buffer, ref remoteEndPoint);

            string receivedMsg = Encoding.UTF8.GetString(buffer, 28, bytesRead);

            Console.WriteLine(DateTime.Now.ToString() + ": Received " + bytesRead + "B from " + remoteEndPoint + ": " + receivedMsg);



            byte[] customResponse = Encoding.UTF8.GetBytes("good day");

            int bytesSent = icmpListener.SendTo(customResponse, remoteEndPoint);        

        }

    }