很奇怪的问题！异步通讯中连接上后一段时间不发送数据再次发送接收不到数据的问题

软件采用异步方式进行通讯，正常情况下连接，发送/接收数据都是正常的

但碰到一个很奇怪的情况，就是当服务端和客户端A在已连接的情况下，如果有十几分钟或更长时间双方没有发送接收任何数据，
然后客户端A再次发送数据给服务端的话，服务端就接收不到了？？？
但更奇怪的是，如果另一个客户端B连接上服务端的时候，并发送数据给服务端后，好像又激活了服务端，然后这两个客户端分别收到了服务端发送过来各自对应的响应数据

难道异步通信中长时间不发送/接收数据会阻塞吗？代码如下，请兄弟姐妹们帮我分析下到底是什么原因造成的，万分感谢！！

//服务端



private Socket _sockSvr;

private const int _buffersize = 2048;

private DataStruct m_DpObj = null;//DataStruct 是个自定义的类



public class DataStruct 

{

        public Socket ClientSocket = null;

        public string ID = string.Empty;

        public byte[] RecvData = new byte[2048];

        public int nReadBytesNums  = 0;

}



public int Start()

 {

       StartListen();



       _sockSvr.BeginAccept(new AsyncCallback(AcceptCallBack), _sockSvr);



       return 1;

}



private void StartListen()

 {

       _sockSvr = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);



       IPEndPoint iep = new IPEndPoint(IPAddress.Any, Port);

       _sockSvr.Bind(iep);



      _sockSvr.Listen(10);

 }



private void AcceptCallBack(IAsyncResult ar)

{

       Socket handler = (Socket)ar.AsyncState;

       Socket _clientSock = handler.EndAccept(ar);



       m_DpObj = new DataStruct ();

       m_DpObj.ClientSocket = _clientSock;

       m_DpObj.ID = GetClientIp(_clientSock);



       _clientSock.BeginReceive(m_DpObj.RecvData, 0, _buffersize, SocketFlags.None, new AsyncCallback(ReceiveData), m_DpObj);

        _sockSvr.BeginAccept(new AsyncCallback(AcceptCallBack), _sockSvr);

}



private void ReceiveData(IAsyncResult ar)

{

       DataStruct ds= ar.AsyncState as DataStruct ;

       Socket tempsocket = ds.ClientSocket;

       ds.nReadBytesNums = ds.ClientSocket.EndReceive(ar);



       if (ds.nReadBytesNums > 0)

       {

               //流程处理，忽略

       }



      ds= new DataStruct ();

      ds.ClientSocket = tempsocket;



      tempsocket.BeginReceive(ds.RecvData, 0, _buffersize, SocketFlags.None, new AsyncCallback(ReceiveData), ds);

      Thread.Sleep(5);

}