程序代码：

       //服务端
namespace Tcp_Server
{
    public partial class Server_ : Form
    {

 
        public Server_()
        {
            InitializeComponent();
        }

        string m_serverIP;
        int m_port;
        TcpListener m_Listener = null;
        IPAddress m_host;
        private void Server__Load(object sender, EventArgs e)
        {
            m_serverIP = txbServerName.Text;//IP地址
            m_host = IPAddress.Parse(m_serverIP);
            m_port = int.Parse(txbPort.Text);//端口
            m_Listener = new TcpListener(m_host, m_port);
            m_Listener.Start();
            MessageBox.Show("开始侦听");
            TcpClient m_client = m_Listener.AcceptTcpClient();
            handle m_handle = new handle();
            m_handle.ClientSocket = m_client;
            Thread m_clientthread = new Thread(new ThreadStart(m_handle.ResponseClient));
            m_clientthread.Start();
            txbShowIFMT.Text += m_handle.m_DataReturn;
        }
    }
    public class handle
    {
        byte[] EncodingASCII(string buf)//将数据转换为ASCII
        {
            byte[] data = Encoding.ASCII.GetBytes(buf);
            return data;
        }

        private TcpClient m_clientsocket;
        public string m_DataReturn, m_DataSend;
        byte[] data;//中间变量

        public TcpClient ClientSocket
        {
            get
            {
                return m_clientsocket;
            }
            set
            {
                m_clientsocket = value;
            }

        }//m_clientsocket属性

        public void ResponseClient()
        {
            StreamReader rs = new StreamReader(m_clientsocket.GetStream());
            m_DataReturn = rs.ReadLine();
            m_DataSend = "收到：" + m_DataReturn;
            NetworkStream ws = m_clientsocket.GetStream();

            data = EncodingASCII(m_DataSend);
            ws.Write(data, 0, data.Length);
        }
    }
}

程序代码：

//客户端
namespace Tcp_Client
{
    public partial class Client_ : Form
    {
        public Client_()
        {
            InitializeComponent();
        }
        static byte[] EncodingASCII(string buf)//将数据转换为ASCII
        {
            byte[] data = Encoding.ASCII.GetBytes(buf);
            return data;
        }

        string FriendServer, DataSend, DataReturn;
        int port;
        TcpClient m_client;
        byte[] data;
        StreamReader rs;//流
        NetworkStream ws;
        private void Client__Load(object sender, EventArgs e)
        {
            FriendServer = txbFriend.Text;
            port = int.Parse(txbPort.Text);//端口
            m_client = new TcpClient();
            m_client.Connect(FriendServer, port);

        }

        private void btnSend_Click(object sender, EventArgs e)
        {

            rs = new StreamReader(m_client.GetStream());
            ws = m_client.GetStream();

            DataSend = txbSend.Text;

            data = EncodingASCII(DataSend);

            ws.Write(data, 0, data.Length);
        }
    }
}