本文共 4986 字，大约阅读时间需要 16 分钟。
着也就意味着你永远不知道哪个异步调用是下一个完毕的调用。可是你能够确定的是它是这4个操作中的一个。
ip::tcp::acceptor acceptor(service, ip::tcp::endpoint(ip::tcp::v4(), 8001)); void handle_accept(talk_to_client::ptr client, const error_code & err) { client->start(); talk_to_client::ptr new_client = talk_to_client::new_(); acceptor.async_accept(new_client->sock(),
boost::bind(handle_accept,new_client,_1));
} int main(int argc, char* argv[]) { talk_to_client::ptr client = talk_to_client::new_(); acceptor.async_accept(client->sock(),boost::bind(handle_accept,client,_1));
service.run();}
class talk_to_client; typedef boost::shared_ptrclient_ptr; typedef std::vector array; array clients;
class talk_to_client : public boost::enable_shared_from_this<talk_to_
client>
, boost::noncopyable { talk_to_client() { ... } public: typedef boost::system::error_code error_code; typedef boost::shared_ptrptr; void start() {
started_ = true; clients.push_back( shared_from_this()); last_ping = boost::posix_time::microsec_clock::local_time(); do_read(); //首先，我们等待客户端连接
} static ptr new_() { ptr new_(new talk_to_client); return new_; } void stop() { if ( !started_) return; started_ = false; sock_.close(); ptr self = shared_from_this(); array::iterator it = std::find(clients.begin(), clients.end(),
self); clients.erase(it);
update_clients_changed(); }
bool started() const { return started_; } ip::tcp::socket & sock() { return sock_;} std::string username() const { return username_; } void set_clients_changed() { clients_changed_ = true; } … private:
ip::tcp::socket sock_; enum { max_msg = 1024 }; char read_buffer_[max_msg]; char write_buffer_[max_msg]; bool started_; std::string username_; deadline_timer timer_; boost::posix_time::ptime last_ping; bool clients_changed_; };
我会用talk_to_client或者talk_to_server来调用connection类，从而使你更明确我所说的内容。
void on_read(const error_code & err, size_t bytes) { if ( err) stop(); if ( !started() ) return; std::string msg(read_buffer_, bytes); if ( msg.find("login ") == 0) on_login(msg); else if ( msg.find("ping") == 0) on_ping(); else if ( msg.find("ask_clients") == 0) on_clients(); } void on_login(const std::string & msg) { std::istringstream in(msg); in >> username_ >> username_; do_write("login ok\n"); update_clients_changed(); } void on_ping() { do_write(clients_changed_ ? "ping client_list_changed\n" : "ping ok\n");
clients_changed_ = false; }
void on_clients() { std::string msg;
for(array::const_iterator b =clients.begin(),e =clients.end(); b != e; ++b)
msg += (*b)->username() + " "; do_write("clients " + msg + "\n"); }
void do_ping() { do_write("ping\n"); } void do_ask_clients() { do_write("ask_clients\n"); } void on_write(const error_code & err, size_t bytes) { do_read(); } void do_read() { async_read(sock_, buffer(read_buffer_), MEM_FN2(read_complete,_1,_2), MEM_FN2(on_read,_1,_2));
post_check_ping(); }
void do_write(const std::string & msg) { if ( !started() ) return; std::copy(msg.begin(), msg.end(), write_buffer_); sock_.async_write_some( buffer(write_buffer_, msg.size()), MEM_FN2(on_write,_1,_2));
} size_t read_complete(const boost::system::error_code & err, size_t bytes) { // ... as before }
void on_check_ping() { ptime now = microsec_clock::local_time(); if ( (now - last_ping).total_milliseconds() > 5000) stop(); last_ping = boost::posix_time::microsec_clock::local_time();
} void post_check_ping() { timer_.expires_from_now(boost::posix_time::millisec(5000));
timer_.async_wait( MEM_FN(on_check_ping)); }
我建议你自己执行这些样例，由于从头到尾读一次代码能加强你对本章展示应用的理解。
我们已经避免了一些诸如内存泄漏和死锁的低级错误。全部的编码都是框架式的。这样你就能够依据你自己的需求对它们进行扩展。