public partial class _Default : System.Web.UI.Page
{
    [DllImport("Iphlpapi.dll")]
    private static extern int SendARP(Int32 dest,Int32 host,ref Int64 mac,ref Int32 length);

    [DllImport("Ws2_32.dll")]
    private static extern Int32 inet_addr(string ip);
    private void Page_Load(object sender, System.EventArgs e)
    {
        // 在此处放置用户代码以初始化页面
        try
        {
            string userip = Request.UserHostAddress;
            string strClientIP = Request.UserHostAddress.ToString().Trim();
            Int32 ldest = inet_addr(strClientIP); //目的地的ip
            Int32 lhost = inet_addr("");   //本地服务器的ip
            Int64 macinfo = new Int64();
            Int32 len = 6;
            int res = SendARP(ldest, 0, ref macinfo, ref len);
            string mac_src = macinfo.ToString("X");
            if (mac_src == "0")
            {
                if (userip == "127.0.0.1")
                    Response.Write("正在访问Localhost!");
                else
                    Response.Write("欢迎来自IP为" + userip + "的朋友！" + "<br>");
                return;
            }

            while (mac_src.Length < 12)
            {
                mac_src = mac_src.Insert(0, "0");
            }

            string mac_dest = "";

            for (int i = 0; i < 11; i++)
            {
                if (0 == (i % 2))
                {
                    if (i == 10)
                    {
                        mac_dest = mac_dest.Insert(0, mac_src.Substring(i, 2));
                    }
                    else
                    {
                        mac_dest = "-" + mac_dest.Insert(0, mac_src.Substring(i, 2));
                    }
                }
            }

            Response.Write("欢迎来自IP为" + userip + "<br>" + ",MAC地址为" + mac_dest + "的朋友！"

             + "<br>");
        }
        catch (Exception err)
        {
            Response.Write(err.Message);
        }
    }

    //以下函数为获取客户端IP
    private string GetClientIP()
    {
        string result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
        if (null == result || result == String.Empty)
        {
            result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
        }

        if (null == result || result == String.Empty)
        {
            result = HttpContext.Current.Request.UserHostAddress;
        }
        return result;
    }

}