TCP网络通信怎么发送数据

TCP网络通信如何发送数据？
小弟刚接触C#，对其概念还不是理解很深，遇到这个问题，请高手赐教，如何执行SendMsg，提示未能实例化？

C# code

        TcpListener dataListener = null;        Socket dataSocket = null;        private void FormMain_Load(object sender, EventArgs e)        {            BeginListen();            tmr.Enabled = true;        }                private void BeginListen()        {            string IP = Dns.GetHostAddresses(Dns.GetHostName())[0].ToString();            IPEndPoint dataEndPoint = new IPEndPoint(IPAddress.Parse(IP), 6005);            dataListener = new TcpListener(dataEndPoint);            dataListener.Start();        }        private void timer1_Tick(object sender, EventArgs e)        {            DataListen();        }        private void DataListen()        {            if (dataListener.Pending())            {                dataSocket = dataListener.AcceptSocket();                //Thread ShowMsgThread = new Thread(new ThreadStart(ShowMsg));                //ShowMsgThread.Start();            }        }        private void ShowMsg()        {            byte[] buffer = new byte[1024 * 1024 * 5];            try            {                while (true)                {                    dataSocket.Receive(buffer);                    string bufferLine = Encoding.Default.GetString(buffer, 0, buffer.Length);                    string[] bufferTine = bufferLine.Split(new string[] { "|" }, StringSplitOptions.None);                                           if (bufferTine[0] == txbIP.Text)                        {                            if (bufferTine[1] == Dns.GetHostAddresses(Dns.GetHostName())[0].ToString())                            {                                if (bufferTine[2] == "connect")                                {                                }                                                            }                        }                }            }            catch (Exception)            {                //异常            }        }        private void SendMsg(string Msg)        {            string ServerIP = Dns.GetHostAddresses(Dns.GetHostName())[0].ToString();            string ClientIP = txbIP.Text;            byte[] SendMsg = Encoding.Default.GetBytes(ServerIP + "|" + ClientIP + "|" + Msg);            dataSocket.Send(SendMsg);        }

C# code

 private void DataListen()        {            if (dataListener.Pending())            {                dataSocket = dataListener.AcceptSocket();            }        }