BBS Server扩展功能应该方便，定义Servlet类，就是以前的state_xxx_xxx回调函数
的演化，状态机。

Servlet Demo:

一个弹出对话框例子：

Screen:
=============================
                                                                                
                        ※          Message           ※                        
                                                                                
                            登录错误，还有 2 机会！                            
                                                                                
                                      确定                                      
                                                                                
Code:
=============================
#ifndef _MESSAGE_BOX_SERVLET_H_
#define _MESSAGE_BOX_SERVLET_H_

#include "servlets.h"

class MessageBoxServlet : public Servlet
{
protected:
    Frame *mainFrame;
    Button *btnOK;
    Label *lMessage;
    String m_message;
public:
    MessageBoxServlet(const String&);
    void init();
    void processEvent(Event);
};

#endif

// $Id: message_box.cpp,v 1.2 2004/04/09 12:55:46 jth Exp $
#include "servlets.h"

MessageBoxServlet::MessageBoxServlet(const String& message)
{
    m_message = message;
}

void MessageBoxServlet::init()
{
    mainFrame = new Frame();
    mainFrame->setTitle("Message");
    mainFrame->setWidth(32);
    mainFrame->setHeight(6);
    mainFrame->setStartRow((m_client->height - mainFrame->height) / 2);
    mainFrame->setStartCol((m_client->width -mainFrame-> width) / 2);

    lMessage = new Label(m_message);
    lMessage->setStyle(Color(black, white, normal));
    btnOK = new Button("  确定  ");

    mainFrame->packWidget("1", btnOK, "buttom", "center");
    mainFrame->packWidget("2", lMessage, "top", "center");
    mainFrame->focusWidget("1");
    mainFrame->signalConnect("1", R_DONE);

    addWidget("w_main_frame", mainFrame);
    focusWidget("w_main_frame");
}

void MessageBoxServlet::processEvent(Event event)
{
    int response = processWidgetEvent(event);
    if (response == R_DONE) {
        m_client->backward();
    }
}
=================
调用:

    String msg = String::format("登录错误，还有 %d 机会！", MAX_LOGIN - mLoginTimes);
    m_client->forward(new MessageBoxServlet(msg));



－－－－－－－－－－－－－－－－－－－－
一个Servlet可以定义static成员变量，供多客户端模式同时服务，比如聊天室servlet
..
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