跪求指点，C#聊天p2p，不知道哪出问题？感激不尽

在form1里new出一个form2实现简单的聊天或者开两个form1程序聊天，老是提示说目标计算机拒绝，无法连接，求帮助啊！

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.Threading;
using System.IO;


namespace WindowsFormsApplication9
{
    public partial class Form1 : Form
    {
        private TcpClient tclient;
       // public Form2 Form2;
        private Thread f1,f2;        
        public Form1()
        {
            InitializeComponent();
     Form2 fm2 = new Form2();
          fm2.Show();           
            /*f3 = new Thread(new ThreadStart());
            f4 = new Thread(new ThreadStart());*/
        }         
        private void Form1_Load(object sender, EventArgs e)
        {   
            button2.Click += new EventHandler(button2_Click);
            f1 = new Thread(new ThreadStart(server));
            f1.Start();        
                  
        }
        private void server()
        {
            TcpListener tlisten = new TcpListener(new IPEndPoint(IPAddress.Any,80));
            tlisten.Start();
            MessageBox.Show("start");
            while (/*f1.IsAlive*/true)
            {
              
                tclient = tlisten.AcceptTcpClient();
                
                    f2 = new Thread(new ThreadStart(receiving));
                    f2.Start();
              
                
                tlisten.Stop();
            }            
        }
        private void receiving()
        {       MessageBox.Show("accept");
                NetworkStream networks = tclient.GetStream();
                try {
                Byte[] receviebytes = new byte[1001];
                int i = networks.Read(receviebytes/*设置缓冲去*/ , 0, receviebytes.Length/*从缓冲大小去多少数*/ );
                string a = Encoding.ASCII.GetString(receviebytes/*设置缓冲去*/, 0, i/*从缓冲大小去多少数*/ );
                MessageBox.Show("yes");
                this.textBox2.Text = this.textBox2.Text + a +" \r\n";//换行
                   }
                catch (Exception e) { MessageBox.Show(e.ToString ());}
                tclient.Close();
                // listBox1.Tag = it.Address.ToString();/*加括号*/ 
        }
        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
               // string host = Dns.GetHostName();
                TcpClient tcent = new TcpClient(Dns .GetHostName (),80);
               /* string host = Dns.GetHostName();
                IPHostEntry s = Dns.GetHostByName(host);
                IPEndPoint it = new IPEndPoint(s.AddressList[0], 80);
                tcent.Connect(it);*/
                NetworkStream networks = tcent.GetStream();
                string t = textBox1.Text;
                Byte[] sendbytes = Encoding.ASCII.GetBytes(t);
                networks.Write(sendbytes, 0, sendbytes.Length);
                textBox1.Clear();
                tcent.Close();
            }
            //MessageBox.Show(" what");
            //tclient.Close();
            catch (Exception g)
            { MessageBox.Show(g.ToString()); }

        }