C# 用Delegate处理UDP数据，怎么调试时无法接收数据呢？

现在的现象是，在VS2005中运行程序，能发出数据包，接收不到任何数据。
如果直接运行exe文件，则没有任何问题。

namespace vpc_sender
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        UDP_Receiver udp = null;
        private void buttonInit_Click(object sender, EventArgs e)
        {
            int myport = int.Parse(textMyPort.Text.Trim());
            udp = new UDP_Receiver(myport);
            udp.OnCommand += new UDP_Receiver.OnCommandDelegate(this.OnReceive);
        }

        void OnReceive(string s)
        {
            textRecText.Text = s;
            textMsg.Text = udp.sMsg;
        }
    }

    public class UDP_Receiver
    {
        UdpClient udp;
        Thread rec_thread;
        public String sCommand, sMsg;
        bool bQuit;

        public delegate void OnCommandDelegate(string s);
        public OnCommandDelegate OnCommand;

        public UDP_Receiver(int my_port)
        {
            try
            {
                udp = new UdpClient(my_port);
                bQuit = false;
                rec_thread = new Thread(receiver);
                rec_thread.Start();
                sMsg = "NET: Start";
                OnCommand = new OnCommandDelegate(EmptyEvent);
            }
            catch
            {
                sMsg = "NET: Init error.";
                udp = null;
            }
        }

        void EmptyEvent(string s)
        { ; }

        private void receiver()
        {
            string msg;
            byte[] buf;
            while (!bQuit)
            {
                try
                {
                    IPEndPoint ip = null;
                    buf = udp.Receive(ref ip);
                    if (buf != null)
                    {
                        msg = Encoding.Default.GetString(buf);
                        OnCommand(msg);
                        sMsg = DateTime.Now.ToShortTimeString() + ":" + msg;
                    }
                    Thread.Sleep(100);
                }
                catch (Exception ex)
                {
                    if (!bQuit)
                        Thread.Sleep(100);
                    sMsg = ex.Message;
                }
            }
            bQuit = false;
        }
    }
} C# 调试 delegate UDP

补充：.NET技术 ,  C#