求助MSDN中关于C#异步SOCKET服务端示例的问题

public class StateObject {

    public Socket workSocket = null;

    public const int BufferSize = 1024;

    public byte[] buffer = new byte[BufferSize];

    public StringBuilder sb = new StringBuilder();  

}



public class AsynchronousSocketListener {

    

    public static string data = null;

    public static ManualResetEvent allDone = new ManualResetEvent(false);



    public AsynchronousSocketListener() {

    }



    public static void StartListening() {

        byte[] bytes = new Byte[1024];



        IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());

        IPAddress ipAddress = ipHostInfo.AddressList[0];

        IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);



        Socket listener = new Socket(AddressFamily.InterNetwork,

            SocketType.Stream, ProtocolType.Tcp );



        try {

            listener.Bind(localEndPoint);

            listener.Listen(100);



            while (true) {

                allDone.Reset();



                Console.WriteLine("Waiting for a connection...");

                listener.BeginAccept( 

                    new AsyncCallback(AcceptCallback),

                    listener );



                allDone.WaitOne();

            }



        } catch (Exception e) {

            Console.WriteLine(e.ToString());

        }



        Console.WriteLine("\nPress ENTER to continue...");

        Console.Read();

    }



    public static void AcceptCallback(IAsyncResult ar) {

        allDone.Set();



        Socket listener = (Socket) ar.AsyncState;

        Socket handler = listener.EndAccept(ar);



        StateObject state = new StateObject();

        state.workSocket = handler;

        handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,

            new AsyncCallback(ReadCallback), state);

    }



    public static void ReadCallback(IAsyncResult ar) {

        String content = String.Empty;

        StateObject state = (StateObject) ar.AsyncState;

        Socket handler = state.workSocket;



        int bytesRead = handler.EndReceive(ar);



        if (bytesRead > 0) {

            state.sb.Append(Encoding.ASCII.GetString(

                state.buffer,0,bytesRead));



            content = state.sb.ToString();

            if (content.IndexOf("<EOF>") > -1) {

                Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",

                    content.Length, content );

                Send(handler, content);

            } else {

                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,

                new AsyncCallback(ReadCallback), state);

            }

        }

    }

    

    private static void Send(Socket handler, String data) {

        byte[] byteData = Encoding.ASCII.GetBytes(data);



        handler.BeginSend(byteData, 0, byteData.Length, 0,

            new AsyncCallback(SendCallback), handler);

    }



    private static void SendCallback(IAsyncResult ar) {

        try {

            Socket handler = (Socket) ar.AsyncState;



            int bytesSent = handler.EndSend(ar);

            Console.WriteLine("Sent {0} bytes to client.", bytesSent);



            handler.Shutdown(SocketShutdown.Both);

            handler.Close();



        } catch (Exception e) {

            Console.WriteLine(e.ToString());

        }

    }





    public static int Main(String[] args) {

        StartListening();

        return 0;

    }

}

以上是MSDN中关于异步SOCLET服务端的代码，我的问题是：
在服务端监听到了一个客户端连接后，将在AcceptCallback函数中创建用户处理这个客户端的对象。并且指定ReadCallback为处理接收的回调函数。
那么ReadCallback函数中的函数过程是否是线程安全的？？比如说：如果第一个客户端连接上来了，并且正在ReadCallback中处理，并且在短时间之内不会结束处理。第2个客户端这时候连接上来了，那么第2个客户端的处理是会等待第一个执行完毕之后才进入ReadCallback呢？还是直接也进入ReadCallback？？如果第2个客户端也进入ReadCallback进行处理了，那么会将第一个客户端的数据冲掉吗？？
另外C#中回调函数的处理机制是否是另外启动一个新的线程？即是否是调用这个回调一次，就会启动一个新的线程来处理这个回调？不过回调也是委托，按照道理来说，应该不会重新启动一个线程的。并且两次调用回调，那么调用的应该是同一个线程中的统一个回调吧。

这个问题困惑了我很久了····请大家帮忙解惑。。。
刚上论坛不久，分不多，请见谅～～～～