private IPEndPoint ipLocalPoint; 
private EndPoint RemotePoint; 
private Socket mySocket; 
private bool RunningFlag = false; 

private string getIPAddress() 
 { 
   // 获得本机局域网IP地址 
   IPAddress[] AddressList = Dns.GetHostByName(Dns.GetHostName()).AddressList; 
   if (AddressList.Length < 1) 
   { 
     return ""; 
   } 
   return AddressList[0].ToString(); 
 } 

private int getValidPort(string port) 
  { 
    int lport; 
    //测试端口号是否有效 
    try 
    { 
      //是否为空 
      if (port == "") 
      { 
        throw new ArgumentException( 
          "端口号无效，不能启动DUP"); 
      } 
      lport = System.Convert.ToInt32(port); 
    } 
    catch (Exception e) 
    { 
      //ArgumentException,  
      //FormatException,  
      //OverflowException 
      Console.WriteLine("无效的端口号：" + e.ToString()); 
      this.tbMsg.AppendText("无效的端口号：" + e.ToString() + "\n"); 
      return -1; 
    } 
    return lport; 
  } 
 
 
  private IPAddress getValidIP(string ip) 
  { 
    IPAddress lip = null; 
    //测试IP是否有效 
    try 
    { 
      //是否为空 
      if (!IPAddress.TryParse(ip, out lip)) 
      { 
        throw new ArgumentException( 
          "IP无效，不能启动DUP"); 
      } 
    } 
    catch (Exception e) 
    { 
      //ArgumentException,  
      //FormatException,  
      //OverflowException 
      Console.WriteLine("无效的IP：" + e.ToString()); 
      this.tbMsg.AppendText("无效的IP：" + e.ToString() + "\n"); 
      return null; 
    } 
    return lip; 
  } 

//得到本机IP，设置UDP端口号   
ip = getValidIP(tbLocalIP.Text); 
port = getValidPort(tbLocalPort.Text); 
ipLocalPoint = new IPEndPoint(ip, port); 
 
//定义网络类型，数据连接类型和网络协议UDP 
mySocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); 
 
//绑定网络地址 
mySocket.Bind(ipLocalPoint); 
 
//得到客户机IP 
ip = getValidIP(tbRemoteIP.Text); 
port = getValidPort(tbRemotePort.Text); 
IPEndPoint ipep = new IPEndPoint(ip, port); 
RemotePoint = (EndPoint)(ipep); 
 
//启动一个新的线程，执行方法this.ReceiveHandle， 
//以便在一个独立的进程中执行数据接收的操作 
 
RunningFlag = true; 
Thread thread = new Thread(new ThreadStart(this.ReceiveHandle)); 
thread.Start(); 

//定义一个委托 
public delegate void MyInvoke(string strRecv); 
private void ReceiveHandle() 
{ 
  //接收数据处理线程 
  string msg; 
  byte[] data=new byte[1024]; 
  MyInvoke myI = new MyInvoke(UpdateMsgTextBox); 
  while (RunningFlag) 
  { 
     
    if (mySocket == null || mySocket.Available < 1) 
    { 
      Thread.Sleep(200); 
      continue; 
    } 
    //跨线程调用控件 
     //接收UDP数据报，引用参数RemotePoint获得源地址 
     int rlen = mySocket.ReceiveFrom(data, ref RemotePoint); 
    msg = Encoding.Default.GetString(data, 0, rlen); 
    tbMsg.BeginInvoke(myI, new object[]{RemotePoint.ToString() + " : " + msg}); 
     
  } 
} 
private void btSend_Click(object sender, EventArgs e) 
{ 
  string msg; 
  msg = tbSendMsg.Text; 
  //发送UDP数据包 
  byte[] data = Encoding.Default.GetBytes(msg); 
  mySocket.SendTo(data, data.Length, SocketFlags.None, RemotePoint); 
} 
private void UpdateMsgTextBox(string msg) 
{ 
  //接收数据显示 
  this.tbMsg.AppendText( msg + "\n"); 
}