求一个c#的UDP客户端程序

private UdpClient client = new UdpClient(12345);
  //ThreadPool.QueueUserWorkItem(recvHandler); // 执行接收数据线程
  private void recvHandler(object obj)
  {
   while (client != null) {
    IPEndPoint ipEP = new IPEndPoint(IPAddress.Any, 0);
    byte[] recvData = client.Receive(ref ipEP);
    if(recvData.Length>0){
     this.Invoke(new Action(AsyncState  =>{
      this.textBox1.Text += Encoding.Default.GetString(AsyncState)+"\r\n"; // 显示接收到的字符串
    }), recvData);
   }
  }
  //向指定客户端发送数据
  private void sendData(byte[] data, string ip, int port)
  {
   client.Send(data, data.Length, new IPEndPoint(IPAddress.Parse(ip), port));
  }

我写在控制程序里了。主程序开启一个新线程做为服务器，在12900端口上收听。之后开始客户端循环，每次输入一行字，发给主机（本例里是同一主机 loopback)

class Program
    {
        static void Main(string[] args)
        {
            // 启动服务器 
            ThreadPool.QueueUserWorkItem(new WaitCallback(RunUdpServer));
            UdpClient uc = new UdpClient(12901);
            // 指定发送的主机名
            IPEndPoint epHost = new IPEndPoint(IPAddress.Loopback, 12900); //127.0.0.1
            while(true)
            {
                Console.Write("输入要发送的内容:");
                string s = Console.ReadLine();
                var data = Encoding.UTF8.GetBytes(s);
                uc.Send(data, data.Length, epHost);
                Thread.Sleep(100);
            }
        }
        private static void RunUdpServer(object para)
        {
            UdpClient uc = new UdpClient(12900);
            // 指定监听的网络区域
            IPEndPoint epListen = new IPEndPoint(IPAddress.Any, 0); //侦听所有的网络活动
            while (true)
            {
                Application.DoEvents();
                try
                {
                    byte[] recb = uc.Receive(ref epListen);
                    Console.WriteLine("Server: recived from {0}:{1}", epListen.Address, epListen.Port); 
                    Console.WriteLine(Encoding.UTF8.GetString(recb));
                }
                catch (Exception ex)
                {
                    Console.WriteLine("出现错误：" + ex.Message.ToString());
                    break;
                }
            }
        }
}