异步，长连接，不知道这样子写对不对，在官网例子的基础上改了一点

大概代码是这样子的，主要改的就是注释的地方

namespace MongoDB_PBAC_Server {     public class StateObject {         public const int BufferSize = 2048;         public byte[] buffer = new byte[BufferSize];         public int length;         public Socket workSocket = null;     }      public class Server {         public static ManualResetEvent allDone = new ManualResetEvent(false);         public static void StartListening() {             IPAddress ipAddress = IPAddress.Parse("127.0.0.1");             int port = 33660;             IPEndPoint point = new IPEndPoint(ipAddress, port);             Socket listener = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);             try {                 listener.Bind(point);                 listener.Listen(100);                 while (true) {                     allDone.Reset();                     listener.BeginAccept(AcceptCallback, listener);                     allDone.WaitOne();                 }             }             catch (Exception e) {  }         }          public static void AcceptCallback(IAsyncResult ar) {             allDone.Set();             Socket listener = (Socket) ar.AsyncState;             Socket handler = listener.EndAccept(ar);             StateObject state = new StateObject();             state.workSocket = handler;             handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, ReadCallback, state);         }          public static void ReadCallback(IAsyncResult ar) {             StateObject state = (StateObject) ar.AsyncState;             Socket handler = state.workSocket;             int bytesRead = handler.EndReceive(ar);             state.length += bytesRead;             if (bytesRead > 0) {                 // 将缓冲区的字节反序列化为消息对象                 Message message = Message.FromBytes(state.buffer);                 if (message != null) {                     byte[] temp = new byte[StateObject.BufferSize];                     // 头部占 5 个字节                     for (int i = 0; i < state.length-(message.length+5); i++) {                         temp[i] = state.buffer[message.length+5 + i];                     }                     state.buffer = temp;                     state.length -= (message.length+5);                     Message res = HandleMessage(message);                     Send(handler, res.ToBytes());                 }                  // 剩下的继续接收                                 handler.BeginReceive(                     state.buffer,                     state .length,                     state.buffer.Length - state.length,                     0,                     ReadCallback,                     state);             }             else {                 // 如果接收字节数为 0，就关闭客户端？                 handler.Shutdown(SocketShutdown.Both);                 handler.Close();             }         }          private static void Send(Socket handler, byte[] data) {             handler.BeginSend(data, 0, data.Length, 0, SendCallback, handler);         }          private static void SendCallback(IAsyncResult ar) {             try {                 Socket handler = (Socket) ar.AsyncState;                 int bytesSent = handler.EndSend(ar);             }catch (Exception e) {}         }          private static Message HandleMessage(Message message) {             return message;         }     } }