判断 TCPClient disconnect

  /// <summary>
  /// Checks the connection state
  /// </summary>
  /// <returns>True on connected. False on disconnected.</returns>
  static bool IsConnected()
  {
   if (_nSocket.Connected)
   {
    if ((_nSocket.Poll(0, SelectMode.SelectWrite)) && (!_nSocket.Poll(0, SelectMode.SelectError)))
    {
     byte[] buffer = new byte[1];
     if (_nSocket.Receive(buffer, SocketFlags.Peek) == 0)
     {
      return false;
     }
     else
     {
      return true;
     }
    }
    else
    {
     return false;
    }
   }
   else
   {
    return false;
   }
  }