using System.Net;
using System.Net.Sockets;
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;


namespace yibutaojie
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        StateObject state;
        private void button2_Click(object sender, System.EventArgs e)
        {
            IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 2012);
            Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            try
            {
                serverSocket.Bind(localEndPoint);
                serverSocket.Listen(100);
                serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), serverSocket);
            }
            catch (Exception ee)
            {
                Console.WriteLine(ee.ToString());
            }
        }
        public void AcceptCallback(IAsyncResult ar)
        {
            Socket serverSocket = (Socket)ar.AsyncState;
            Socket clientSocket = serverSocket.EndAccept(ar);
            state = new StateObject();
            state.workSocket = clientSocket;
            Send("连接服务器成功");
            clientSocket.BeginReceive(state.buffer,0,StateObject.BufferSize,0,new AsyncCallback(ReadCallback),state);
        }
        public void ReadCallback(IAsyncResult ar)
        {
            StateObject state = (StateObject)ar.AsyncState;
            Socket clientSocket = state.workSocket;
            int bytesRead = clientSocket.EndReceive(ar);
            if (bytesRead > 0)
            {
                String str = Encoding.Unicode.GetString(state.buffer, 0, bytesRead);
                textBox1.AppendText("客户端对服务器说：" + str + "\r\n");
            }
                clientSocket.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
            }
            private void Send(String data)
            {
                byte[] byteData=Encoding.Unicode.GetBytes(data);
                state.workSocket.BeginSend(byteData,0,byteData.Length,0,new AsyncCallback(SendCallback),state);
            }
            private void SendCallback(IAsyncResult ar)
           {
                try
               {
                   Socket clientSocket=(Socket) ar.AsyncState;
                   int bytesSent=clientSocket.EndSend(ar);
               }
               catch(Exception e)
               {
                   Console.WriteLine(e.ToString());
               }
           }
           private void button1_Click(object sender,System.EventArgs e)
          {
              textBox1.AppendText("服务器对客户端说:"+textBox2.Text+"\r\n");
              Send(textBox2.Text); 
          }
          private void Form1_Closing(object sender,System.ComponentModel.CancelEventArgs e)
         {
             try
             {
                 state.workSocket.Shutdown(SocketShutdown.Both);
                 state.workSocket.Close();
             }
             catch (Exception){}
         }
        }
    public class StateObject
    {
        public Socket workSocket = null;
        public const int BufferSize = 1024;
        public byte[] buffer = new byte[BufferSize];
    }
}
提示说是“未将对象引用设置到对象的实例”，我查不出错，求高手指点。

serverSocket.BeginAccept(new AsyncCallback([color=#FF0000]AcceptCallback[/color]), serverSocket);

------解决方案--------------------