问为什么我的线程不能连续工作

EN

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Threading;


namespace MultiClientServer
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }



        private void button1_Click(object sender, EventArgs e)
        {
            TcpListener listner = new TcpListener(new IPEndPoint(IPAddress.Loopback, 8000));
            listner.Start();
            textBox1.Text += "Started TCP Server"+Environment.NewLine;
            listner.BeginAcceptTcpClient(new AsyncCallback(Accept), listner);
        }

        void Accept(IAsyncResult result)
        {
            textBox1.Invoke(new MethodInvoker(delegate()
                {
                    textBox1.Text += "Client Request Arrived" + Environment.NewLine;
                }));
            TcpListener listner1 = (TcpListener)result.AsyncState;
            TcpClient client = listner1.EndAcceptTcpClient(result);
            textBox1.Invoke(new MethodInvoker(delegate()
                {
                    textBox1.Text += "Client Request Approved" + Environment.NewLine;
                }));
            Thread th = new Thread(new ParameterizedThreadStart(ContinueRcv));
            th.Start(client);
        }

        void ContinueRcv(object obj)
        {
            TcpClient client = (TcpClient)obj;
            StreamReader sr = new StreamReader(client.GetStream());
            textBox1.Invoke(new MethodInvoker(delegate()
                {
                    textBox1.Text += sr.ReadLine() + Environment.NewLine;
                }));
        }
    }
}