public partial class Form2 : Form
    {

        //聲明監聽對象
        private TcpListener tl;

        //聲明網絡流
        private NetworkStream ns;
        public Form1()
        {
            CheckForIllegalCrossThreadCalls = false;
            InitializeComponent();           
        }

        private void btnStart_Click(object sender, EventArgs e)
        {

            //開啟8888端口的監聽
            tl = new TcpListener(8888);
            tl.Start();

            //開啟線程
            Thread th = new Thread(new ThreadStart(listen));
            th.IsBackground = true;
            th.Start();
        }
        private void listen()
        {           
            while (true)
            {   

                //獲得響應的Socket
                Socket sock = tl.AcceptSocket();  

                //通過該Socket實例化網絡流           
                ns = new NetworkStream(sock);

                //ClientTcp是添加的類，下面會做說明
                ClientTcp ct = new ClientTcp(ns);

                //ct_MyEvent方法注冊ClientTcp類的MyEvent事件
                ct.MyEvent += new MyDelegate(ct_MyEvent);

                //開啟線程
                Thread th = new Thread(new ThreadStart(ct.TcpThread));
                th.IsBackground = true;
                th.Start();
            }
        }

        void ct_MyEvent(string temp)
        {

            //設置服務器端TextBox的值
            this.textBox1.Text = temp;
        }
    }

public partial class Form1 : Form
    {

        //聲明Tcp客戶端
        private TcpClient tc;

        //聲明網絡流
        private NetworkStream ns;
        public Form1()
        {
            CheckForIllegalCrossThreadCalls = false;
            InitializeComponent();
        }

        private void button2_Click(object sender, EventArgs e)
        {

            //注冊本機8888端口
            tc = new TcpClient("localhost",8888);

            //實例化網絡流對象
            ns = tc.GetStream();
            string temp = this.textBox1.Text;

            StreamWriter sw = new StreamWriter(ns);
            StreamReader sr = new StreamReader(ns);

            //將TextBox1的值傳給服務器端
            sw.WriteLine(temp);
            sw.Flush();

            //接收服務器端回傳的字符串
            string str = sr.ReadLine();
            this.textBox2.Text = str;
            sr.Close();
            sw.Close();
        }
    }

    //聲明一個需要一個字符串參數的委托

    public delegate void MyDelegate(string temp);
    class ClientTcp
    {

        //設置網絡流局部對象
        private NetworkStream ns;

        //聲明類型為MyDelegate的事件MyEvent
        public event MyDelegate MyEvent;

        //構造函數中接收參數以初始化
        public ClientTcp(NetworkStream ns)
        {
            this.ns = ns;
        }

        //服務器端線程所調用的方法
        public void TcpThread()
        {

            //獲得相關的封裝流
            StreamReader sr = new StreamReader(ns);
            string temp = sr.ReadLine();

            //接收到客戶端消息后觸發事件將消息回傳
            MyEvent(temp);
            StreamWriter sw = new StreamWriter(ns);

            //轉換為大寫后發送消息給客戶端
            sw.WriteLine(temp.ToUpper());
            sw.Flush();
            sw.Close();
            sr.Close();
        }
    }