boost.asio包装类st_asio_wrapper开发教程（2015.11.6更新）（二）

如果你是偶然浏览到这里，请先看  boost.asio包装类st_asio_wrapper开发教程（一）
源代码及例程下载地址:
git: https://github.com/youngwolf-project/st_asio_wrapper/，另外，我的资源里面也有下载，但不是最新的。
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六：开发教程（服务端）
服务端直接#include st_asio_wrapper_server.h，就可实现一个简单的服务端了，如下（还演示了一个echo服务器，所以继承自st_server_base写了个echo_server类）：

//configuration
#define SERVER_PORT		9527
#define REUSE_OBJECT //use objects pool
//#define FORCE_TO_USE_MSG_RECV_BUFFER //force to use the msg recv buffer
#define ENHANCED_STABILITY
//configuration

#include "st_asio_wrapper_server.h"
using namespace st_asio_wrapper;

#define QUIT_COMMAND	"quit"
#define RESTART_COMMAND	"restart"
#define LIST_ALL_CLIENT	"list_all_client"
#define LIST_STATUS		"status"
#define SUSPEND_COMMAND	"suspend"
#define RESUME_COMMAND	"resume"

//demonstrate how to use custom packer
//in the default behavior, every st_tcp_socket has their own packer, and cause memory waste
//at here, we make every echo_socket use the same global packer for memory saving
//notice: do not do this for unpacker, because unpacker has member variables and can't share each other
auto global_packer(boost::make_shared<packer>());

//demonstrates how to control the type of st_server_socket_base::server from template parameters
class i_echo_server : public i_server
{
public:
	virtual void test() = 0;
};

class echo_socket : public st_server_socket_base<DEFAULT_PACKER, DEFAULT_UNPACKER, i_echo_server>
{
public:
	echo_socket(i_server& server_) : st_server_socket_base(server_) {inner_packer(global_packer);}

public:
	//because we use objects pool(REUSE_OBJECT been defined), so, strictly speaking, this virtual
	//function must be rewrote, but we don't have member variables to initialize but invoke father's
	//reset() directly, so, it can be omitted, but we keep it for possibly future using
	virtual void reset() {st_server_socket_base::reset();}

protected:
	virtual void on_recv_error(const error_code& ec)
	{
		//the type of st_server_base::server now can be controled by derived class(echo_socket),
		//which is actually i_echo_server, so, we can invoke i_echo_server::test virtual function.
		server.test();
		st_server_socket_base::on_recv_error(ec);
	}

	//msg handling: send the original msg back(echo server)
#ifndef FORCE_TO_USE_MSG_RECV_BUFFER
	//this virtual function doesn't exists if FORCE_TO_USE_MSG_RECV_BUFFER been defined
	virtual bool on_msg(out_msg_type& msg) {return post_msg(msg.data(), msg.size());}
#endif
	//we should handle the msg in on_msg_handle for time-consuming task like this:
	virtual bool on_msg_handle(out_msg_type& msg, bool link_down) {return send_msg(msg.data(), msg.size());}
	//please remember that we have defined FORCE_TO_USE_MSG_RECV_BUFFER, so, st_tcp_socket will directly
	//use the msg recv buffer, and we need not rewrite on_msg(), which doesn't exist any more
	//msg handling end
};

class echo_server : public st_server_base<echo_socket, st_object_pool<echo_socket>, i_echo_server>
{
public:
	echo_server(st_service_pump& service_pump_) : st_server_base(service_pump_) {}

	//from i_echo_server, pure virtual function, we must implement it.
	virtual void test() {/*puts("in echo_server::test()");*/}
};

int main() {
	puts("type quit to end these two servers.");

	std::string str;
	st_service_pump service_pump;
	st_server server_(service_pump); //only need a simple server? you can directly use st_server
	server_.set_server_addr(SERVER_PORT + 100);
	echo_server echo_server_(service_pump); //echo server

	service_pump.start_service(1);
	while(service_pump.is_running())
	{
		std::cin >> str;
		if (str == QUIT_COMMAND)
			service_pump.stop_service();
		else if (str == RESTART_COMMAND)
		{
			service_pump.stop_service();
			service_pump.start_service(1);
		}
		else if (str == LIST_STATUS)
		{
			printf("normal server:\nvalid links: " size_t_format ", closed links: " size_t_format "\n",
				server_.size(), server_.closed_object_size());

			printf("echo server:\nvalid links: " size_t_format ", closed links: " size_t_format "\n",
				echo_server_.size(), echo_server_.closed_object_size());
		}
		//the following two commands demonstrate how to suspend msg dispatching, no matter recv buffer been used or not
		else if (str == SUSPEND_COMMAND)
			echo_server_.do_something_to_all(boost::bind(&echo_socket::suspend_dispatch_msg, _1, true));
		else if (str == RESUME_COMMAND)
			echo_server_.do_something_to_all(boost::bind(&echo_socket::suspend_dispatch_msg, _1, false));
		else if (str == LIST_ALL_CLIENT)
		{
			puts("clients from normal server:");
			server_.list_all_object();
			puts("clients from echo server:");
			echo_server_.list_all_object();
		}
		else
			server_.broadcast_msg(str);
	}
	return 0;
}

//restore configuration
#undef SERVER_PORT
#undef REUSE_OBJECT //use objects pool
#undef FORCE_TO_USE_MSG_RECV_BUFFER //force to use the msg recv buffer
#undef ENHANCED_STABILITY
//restore configuration

        以上例子中，服务端从控制台接收数据，调用broadcast_msg广播数据；当收到数据时，normal server会输出到控制台（st_tcp_socket实现）；

        其中st_server server_;这行申请了一个普通的服务端，它的功能仅仅是接受连接，发送接收消息等。一般来说，需要从st_server_socket继承一个自己的套接字类，从st_server继承一个服务类。为此，服务端demo还演示了一个echo服务器，它会把收到的任何数据发送回去（大家可以学着做一个echo客户端，但不要echo服务端与echo客户端一同工作，否则就死循环了。
        start_service开启服务，stop_service结束服务（退出时必须明确调用），is_running判断服务的运行状态；如果想修改服务端地址，则在调用start_service之前调用set_server_addr函数；
        stop_service之后，可再次调用start_service开启服务；
        注意：st_server的del_client一般用于服务端被动删除某个client（即在错误发生的时候，比如在st_tcp_socket的on_recv_error和on_send_error里面调用，参看st_server_socket）；服务端如果想主动关闭某个client，建议调用这个client的force_close或者graceful_close（st_tcp_socket实现）函数，它们的调用最终会促使on_recv_error的调用；
        st_server的close_all_client主动关闭所有client，比如服务端退出的时候（stop_service会自动调用）；
        重写st_server的on_accept函数，根据你自己的策略确定是否接受客户端的连接，接受返回true；
        st_server维护了一个链表（st_object_pool实现）用于保存所有的client（这样带几个好处：一、在广播消息的时候，很方便；二、可开启类似垃圾回收机制的自动清理已经关闭的连接的功能；三、可开启对象池功能），如果你想自己管理这些client，可以在on_accept里面返回false，然后把它保存在自己的容器里面，并调用start（st_server_socket实现）以便开始接受数据（ 只调用一次即可）；
        当然，你还可以在返回true的同时，自己也保存一份client（ 此时就不要再调用start了），这样做不会带来多少内存消耗，因为它是用智能指针包装的，复制一份只是增加一个引用计数。至于这样做有什么好处，如果你想不到，说明你不需要，当你有需求的时候，你自然而然就会知道有什么用了，我在这里只是告诉大家可以这样做，有个印象即可；
        关于是重写on_msg还是on_msg_handle，请参看教程 第四篇。