udpclient之异步编程

  首先，自定义一个类，这了类之后会用到。

class UdpState
    {
        public UdpClient u;
        public IPEndPoint e;
    }

以下是主要代码，虽然是用udpclient来编程，但是这是编写的Server端代码，主要用到了异步接收方发，具体的方法讲解可以在MSDN上查看：

        public static void ReceiveCallback(IAsyncResult ar)
        {
            UdpClient u = (UdpClient)((UdpState)(ar.AsyncState)).u;
            IPEndPoint e = (IPEndPoint)((UdpState)(ar.AsyncState)).e;

            Byte[] receiveBytes = u.EndReceive(ar, ref e);
            string receiveString = Encoding.ASCII.GetString(receiveBytes);

            Console.WriteLine("Received: {0}", receiveString);
            messageReceived = true;
        }

        public static void ReceiveMessages()
        {
              int listenPort=11000;
            // Receive a message and write it to the console.
            IPEndPoint e = new IPEndPoint(IPAddress.Any, listenPort);
            UdpClient u = new UdpClient(e);

            UdpState s = new UdpState();//此处用到了自定义的类
            s.e = e;
            s.u = u;

            Console.WriteLine("listening for messages");
            u.BeginReceive(new AsyncCallback(ReceiveCallback), s);

            // Do some work while we wait for a message. For this example,
            // we'll just sleep
            while (!messageReceived)
            {
                Thread.Sleep(10000);
            }
        }