TCP套接字没有响应

我正在使用C#套接字编程开发TCP客户端/服务器应用程序。有时，我会遇到一个非常奇怪的问题，因为服务器（windows服务）正在端口（8089）上运行，但它没有监听任何客户端请求，当我用端口扫描仪测试端口时，它告诉我端口没有响应！这是我的服务器代码：

首先，

private void MainThread（）{byte[]字节=新字节[1024]；

        IPEndPoint localEndPoint = new IPEndPoint(0, this.port);
        Socket listener = new Socket(AddressFamily.InterNetwork,
            SocketType.Stream, ProtocolType.Tcp );
        try {
            listener.Bind(localEndPoint);
            listener.Listen(100);
            while (active) {
                mainDone.Reset();
                listener.BeginAccept(new AsyncCallback(AcceptCallback),listener);
                while (active)
                    if (mainDone.WaitOne(100, true))
                        break;
            }
            listener.Close();
        } catch (Exception e) {
            if (OnError != null)
                OnError(this, e.ToString());
            LogManager.LogError(e, "TCPSimpleServer MainThread"); 
        }

然后，

 private void AcceptCallback(IAsyncResult ar) {
        Socket handler = null;
        try
        {
            mainDone.Set();
            Socket listener = (Socket)ar.AsyncState;
            handler = listener.EndAccept(ar);
            if (OnConnect != null)
                OnConnect(this, handler);
            StateObject state = new StateObject();
            state.workSocket = handler;
            state.endPoint = (IPEndPoint)handler.RemoteEndPoint;
            stateObjectDictionary.Add(state, state.workSocket);
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
        }
        catch (ObjectDisposedException)
        {
            // Connection closed by client
            if (OnDisconnect != null)
                OnDisconnect(this, (IPEndPoint)handler.RemoteEndPoint);
            return;
        }
        catch (Exception ex)
        {
            LogManager.LogError(ex, "TCPSimpleServer AcceptCallback");
            return;
        }

最后，

private void ReadCallback(IAsyncResult ar) {
        try
        {
            String content = String.Empty;
            StateObject state = (StateObject)ar.AsyncState;
            Socket handler = state.workSocket;
            int bytesRead = 0;
            try
            {
                bytesRead = handler.EndReceive(ar);
            }
            catch (Exception ex)
            {
                // Connection closed by client
                if (OnDisconnect != null)
                    OnDisconnect(this, state.endPoint);
                handler.Close();
                return;
            }
            if (bytesRead > 0)
            {
                string data = Encoding.Default.GetString(state.buffer, 0, bytesRead);
                if (OnDataAvailable != null)
                    OnDataAvailable(this, handler, data);
                try
                {
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                        new AsyncCallback(ReadCallback), state);
                }
                catch (Exception e)
                {
                    if (OnError != null)
                        OnError(this, e.Message);
                    LogManager.LogError(e, "TCPSimpleServer ReadCallback");
                    handler.Close();
                }
            }
            else
            {
                // Connection closed by peer
                if (OnDisconnect != null)
                    OnDisconnect(this, state.endPoint);
            }
        }
        catch (Exception ex)
        {
            LogManager.LogError(ex, "TCPSimpleServer ReadCallback");
        }
    }

我认为问题出在最后一个方法ReadCallback（）中。如果在EndReceive（）方法中出现问题，套接字（处理程序）永远不会释放端口。有什么帮助吗？

while (active) 
    if (mainDone.WaitOne(100, true)) 
        break;