void SendMsg(string toip, int port )

        {

            try

            {

                string message="发送内容";

                UdpClient udpclient = new UdpClient();

                IPEndPoint ipendpoint = new IPEndPoint(IPAddress.Parse(ip), port);              

                byte[] data = Encoding.Default.GetBytes(message);

                udpclient.Send(data, data.Length, ipendpoint);

                udpclient.Close();

            }

            catch (Exception ex)

            {

                MessageBox.Show("UDP发送数据" + ex.ToString());

            }

        }

 public UdpService udp;

a>实例化、初始化接收事件

udp = new UdpService(fromip, , "127.0.0.1", );

udp.EvtGetValues+=new UdpService.GetRecevice(udp_EvtGetValues);

b>启动UDP

udp.TurnOn();

c>停止UDP

 udp.TurnOff();

d>接收事件处理

 void udp_EvtGetValues(byte[] ReceviceBuff)

        {

            //string message = Encoding.UTF8.GetString(ReceviceBuff, 0, ReceviceBuff.Length);

           //可接收中文内容

           Encoding ei=Encoding.GetEncoding();

            string message = ei.GetString(ReceviceBuff, , ReceviceBuff.Length);

            if (message.Length > )

            {

              // 处理接收逻辑

            }

        }

 public  class UdpService

    {

        #region 内部变量

        string devIP = "127.0.0.1";

        int devPort = ;

        UdpClient mySocket;

        string meIP = "127.0.0.1";

        int mePort = ;

        IPEndPoint RemotePoint;

        bool isRunning = false;

        bool isOpen = false;

        List<Thread> listThread = new List<Thread>();

        string icId = "";

        string cardContent = "";

        byte[] cardContentBuf;

        #endregion

        public UdpService(string ServerIP, int ServerPort, string DevIP, int DevPort)

        {

            this.meIP = ServerIP;

            this.mePort = ServerPort;

            this.devIP = DevIP;

            this.devPort = DevPort;           

        }

        #region   

        public void TurnOn()

        {

            try

            {

                if (isOpen) return;

                mySocket = new UdpClient(mePort);

                IPEndPoint ipLocalPoint = new IPEndPoint(IPAddress.Parse(meIP), mePort);

                RemotePoint = new IPEndPoint(IPAddress.Any, devPort);

                isRunning = true;

                Thread thread = new Thread(new ThreadStart(this.ReceiveHandle));

                thread.IsBackground = true;

                thread.Start();

                listThread.Add(thread);

                isOpen = true;

            }

            catch (Exception ex)

            {

                isOpen = false;

                throw new Exception(ex.Message);

            }

        }

        public void TurnOff()

        {

            try

            {

                isOpen = false;

                isRunning = false;

                for (int i = ; i < listThread.Count; i++)

                {

                    try

                    {

                        listThread[i].Abort();

                    }

                    catch (Exception) { }

                }

                if (mySocket != null)

                {

                    mySocket.Close();

                }

            }

            catch (Exception)

            {

            }

        }

        public delegate void GetRecevice(byte[] ReceviceBuff);

        public event GetRecevice EvtGetValues;

        private void ReceiveHandle()

        {

            byte[] sendbuf = new byte[];

            byte[] sendwritbuf = new byte[];

            while (isRunning)

            {

                try

                {

                    if (mySocket == null || mySocket.Available < )

                    {

                        Thread.Sleep();

                        continue;

                    }

                    //接收UDP数据报，引用参数RemotePoint获得源地址

                    byte[] buf = mySocket.Receive(ref RemotePoint);

                    if (devIP == null || devIP.Length < )

                    {

                        devIP = RemotePoint.Address.ToString();

                        devPort = RemotePoint.Port;

                    }

                    if (EvtGetValues != null)

                    {

                        EvtGetValues(buf);

                    }

                }

                catch (Exception)

                {

                }

            }

        }

        #endregion

    }