c# UDP通信

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private UdpClient sendUdpClient;
        private UdpClient receiveUpdClient;
        public Form1()
        {
            InitializeComponent();
            IPAddress[] ips = Dns.GetHostAddresses("");
            tbxlocalip.Text = ips[0].ToString();
            int port = 51883;
            tbxlocalPort.Text = port.ToString();
            tbxSendtoIp.Text = ips[0].ToString();
           tbxSendtoport.Text = port.ToString();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Control.CheckForIllegalCrossThreadCalls = false;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (tbxMessageSend.Text == string.Empty)
            {
                MessageBox.Show("发送内容不能为空", "提示");
                return;
            }

            // 选择发送模式
            if (chkbxAnonymous.Checked == true)
            {
                // 匿名模式(套接字绑定的端口由系统随机分配)
                sendUdpClient = new UdpClient(0);
            }
            else
            {
                // 实名模式(套接字绑定到本地指定的端口)
                IPAddress localIp = IPAddress.Parse(tbxlocalip.Text);
                IPEndPoint localIpEndPoint = new IPEndPoint(localIp, int.Parse(tbxlocalPort.Text));
                sendUdpClient = new UdpClient(localIpEndPoint);
            }

            Thread sendThread = new Thread(SendMessage);
            sendThread.Start(tbxMessageSend.Text);
        }

        private void SendMessage(object obj)
        {
            string message = (string)obj;
            byte[] sendbytes = Encoding.Unicode.GetBytes(message);
            IPAddress remoteIp = IPAddress.Parse(tbxSendtoIp.Text);
            IPEndPoint remoteIpEndPoint = new IPEndPoint(remoteIp, int.Parse(tbxSendtoport.Text));
            sendUdpClient.Send(sendbytes, sendbytes.Length, remoteIpEndPoint);

            sendUdpClient.Close();

            // 清空发送消息框
            //ResetMessageText(tbxMessageSend);
        }

        delegate void ShowMessageforViewCallBack(ListBox listbox, string text);
        private void ShowMessageforView(ListBox listbox, string text)
        {
            if (listbox.InvokeRequired)
            {
                ShowMessageforViewCallBack showMessageforViewCallback = ShowMessageforView;
                listbox.Invoke(showMessageforViewCallback, new object[] { listbox, text });
            }
            else
            {
                lstbxMessageView.Items.Add(text);
                lstbxMessageView.SelectedIndex = lstbxMessageView.Items.Count - 1;
                lstbxMessageView.ClearSelected();
            }
        }

        //delegate void ResetMessageCallback(TextBox textbox);
        //private void ResetMessageText(TextBox textbox)
        //{
        //    // Control.InvokeRequired属性代表
        //    // 如果控件的处理与调用线程在不同线程上创建的，则为true,否则为false
        //    if (textbox.InvokeRequired)
        //    {
        //        ResetMessageCallback resetMessagecallback = ResetMessageText;
        //        textbox.Invoke(resetMessagecallback, new object[] { textbox });
        //    }
        //    else
        //    {
        //        textbox.Clear();
        //        textbox.Focus();
        //    }
        //}

        private void button4_Click(object sender, EventArgs e)
        {
            // 创建接收套接字
            IPAddress localIp = IPAddress.Parse(tbxlocalip.Text);
            IPEndPoint localIpEndPoint = new IPEndPoint(localIp, int.Parse(tbxlocalPort.Text));
            receiveUpdClient = new UdpClient(localIpEndPoint);

            Thread receiveThread = new Thread(ReceiveMessage);
            receiveThread.Start();
        }
        private void ReceiveMessage()
        {
            IPEndPoint remoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
            while (true)
            {
                try
                {
                    // 关闭receiveUdpClient时此时会产生异常
                    byte[] receiveBytes = receiveUpdClient.Receive(ref remoteIpEndPoint);

                    string message = Encoding.Unicode.GetString(receiveBytes);

                    // 显示消息内容
                    ShowMessageforView(lstbxMessageView, string.Format("{0}[{1}]", remoteIpEndPoint, message));
                }
                catch
                {
                    break;
                }
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            receiveUpdClient.Close();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.lstbxMessageView.Items.Clear();
        }
    }
}