之前用UdpClient，发现当开了一个端口用于监听接收，则不能再用来发送（反之亦然）。这样对于简单的收发信息来说无问题，但如果需要nat穿透的程序，则变得困难。用Socket类则不存在该问题，参考下面示例代码：

??? class Program
??? {
??????? static void Main(string[] args)
??????? {
??????????? SocketTest test = new SocketTest();
??????????? test.StartReceive();
??????????? Console.WriteLine("请输入对端口号，准备发送：");
??????????? string port = Console.ReadLine();
??????????? test.SendData(Encoding.UTF8.GetBytes("你好吗？"), IPAddress.Parse("127.0.0.1"), Convert.ToInt32(port));
??????????? Console.ReadKey(true);
??????? }

????????
??? }

??? public class SocketTest
??? {
??????? private Socket _socket;
??????? IPEndPoint _local = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 5238);
??????? Thread _receiveThread = null;

??????? public void StartReceive()
??????? {
??????????? _socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
??????????? _receiveThread = new Thread(Receive);
??????????? _receiveThread.Start();
??????? }

??????? public void SendData(byte[] data, IPAddress remoteIP, int remotePort)
??????? {
??????????? _socket.SendTo(data, new IPEndPoint(remoteIP, remotePort));
??????? }

??????? public void Close()
??????? {
??????????? if (_receiveThread != null)
??????????????? _receiveThread.Abort();
??????????? if (_socket != null)
??????????????? _socket.Close();
??????? }

??????? private void Receive()
??????? {
??????????? _socket.Bind(_local);
??????????? Console.WriteLine("开始接收。。。");
??????????? while (true)
??????????? {
??????????????? byte[] buffer = new byte[1024];
??????????????? EndPoint remoteEP = (EndPoint)(new IPEndPoint(IPAddress.Any, 0));
??????????????? int len = _socket.ReceiveFrom(buffer, ref remoteEP);
??????????????? IPEndPoint ipEndPoint = remoteEP as IPEndPoint;
??????????????? Console.WriteLine("收到消息：客户机IP--{0}，，端口--{1}", ipEndPoint.Address.ToString(), ipEndPoint.Port.ToString());
??????????????? Console.WriteLine("消息内容：{0}", Encoding.UTF8.GetString(buffer, 0, len));
??????????? }
??????? }

????????
??? }

转载：?http://harvey8819.blog.163.com/blog/static/162365181201123121635983/