private void ConnectionChecker()
        {
            while (Activated)
            {
                if (_user.CountSend() == 0)
                {
                    Packet connectionCheckPacket = new Packet
                    {
                        Data         = new byte[1],
                        DataSize     = 1,
                        FileType     = (byte)FileType.NoFile,
                        MorePackets  = false,
                        PacketNumber = 0,
                        ProcessId    = 0,
                        RequestType  = (byte)PacketType.ConnectionCheck
                    };
                    MakePacketHeader(connectionCheckPacket);
                    connectionCheckPacket.Data[0] = (byte)PacketType.ConnectionCheck;
                    _user.EnqueueSend(connectionCheckPacket);
                }

                Thread.Sleep(CheckSendTimeInterval); //wait
            }
        }