C#用UDP同步发送数据和接受数据

using System;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace UdpChatExample
{
public partial class FormChat : Form
{
/// <summary>接收用</summary>
private UdpClient receiveUdpClient;
/// <summary>发送用</summary>
private UdpClient sendUdpClient;
/// <summary>和本机绑定的端口号</summary>
private const int port = 18001;
/// <summary>本机IP</summary>
IPAddress ip;
/// <summary>远程主机IP</summary>
IPAddress remoteIp;

public FormChat()
{
InitializeComponent();

//获取本机可用IP地址
IPAddress[] ips = Dns.GetHostAddresses(Dns.GetHostName());
ip = ips[ips.Length - 1];
//为了在同一台机器调试，此IP也作为默认远程IP
remoteIp = ip;
textBoxRemoteIP.Text = remoteIp.ToString();
textBoxSend.Text = "你好！";
}
private void FormChat_Load(object sender, EventArgs e)
{
//创建一个线程接收远程主机发来的信息
Thread myThread = new Thread(ReceiveData);

//将线程设为后台运行
myThread.IsBackground = true;
myThread.Start();
textBoxSend.Focus();
}
private void ReceiveData()//接收数据
{
IPEndPoint local = new IPEndPoint(ip, port);
receiveUdpClient = new UdpClient(local);
IPEndPoint remote = new IPEndPoint(IPAddress.Any, 0);
while (true)
{
try
{
//关闭udpClient时此句会产生异常
byte[] receiveBytes = receiveUdpClient.Receive(ref remote);
string receiveMessage = Encoding.Unicode.GetString(
receiveBytes, 0, receiveBytes.Length);
AddItem(listBoxReceive, string.Format("来自{0}：{1}", remote, receiveMessage));
}
catch
{
break;
}
}
}

private void buttonSend_Click(object sender, EventArgs e)
{
Thread t = new Thread(SendMessage);//新建发送数据线程
t.IsBackground = true;
t.Start(textBoxSend.Text);
}
/// <summary>发送数据到远程主机</summary>
private void SendMessage(object obj)
{
string message = (string)obj;
sendUdpClient = new UdpClient(0);
byte[] bytes = System.Text.Encoding.Unicode.GetBytes(message);
IPEndPoint iep = new IPEndPoint(remoteIp, port);
try
{
sendUdpClient.Send(bytes, bytes.Length, iep);
AddItem(listBoxStatus, string.Format("向{0}发送：{1}", iep, message));
ClearTextBox();
}
catch (Exception ex)
{
AddItem(listBoxStatus, "发送出错:" + ex.Message);
}
}

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

delegate void ClearTextBoxDelegate();
private void ClearTextBox()
{
if (textBoxSend.InvokeRequired)
{
ClearTextBoxDelegate d = ClearTextBox;
textBoxSend.Invoke(d);
}
else
{
textBoxSend.Clear();
textBoxSend.Focus();
}
}
}
}