【发布时间】：2016-03-03 13:00:47
【问题描述】：
我的应用程序基于 asio 聊天示例，由客户端和服务器组成： - 客户端：连接到服务器，接收请求并响应它 - 服务器：有一个 QT GUI（主线程）和一个网络服务（单独的线程）监听连接，向特定客户端发送请求并解释来自/在 GUI 中的响应
我想以异步方式实现这一点，以避免每个客户端连接使用单独的线程。
在我的 QT 窗口中，我有一个 io_service 实例和一个我的网络服务实例：
io_service_ = new asio::io_service();
asio::ip::tcp::endpoint endpoint(asio::ip::tcp::v4(), "1234");
service_ = new Service(*io_service_, endpoint, this);
asio::io_service* ioServicePointer = io_service_;
t = std::thread{ [ioServicePointer](){ ioServicePointer->run(); } };
我希望能够向一个客户端发送数据，如下所示：
service_->send_message(selectedClient.id, msg);
我正在通过观察者模式接收和处理响应（窗口实现 IStreamListener 接口）
Service.cpp：
#include "Service.h"
#include "Stream.h"
void Service::runAcceptor()
{
acceptor_.async_accept(socket_,
[this](asio::error_code ec)
{
if (!ec)
{
std::make_shared<Stream>(std::move(socket_), &streams_)->start();
}
runAcceptor();
});
}
void Service::send_message(std::string streamID, chat_message& msg)
{
io_service_.post(
[this, msg, streamID]()
{
auto stream = streams_.getStreamByID(streamID);
stream->deliver(msg);
});
}
流.cpp：
#include "Stream.h"
#include <iostream>
#include "../chat_message.h"
Stream::Stream(asio::ip::tcp::socket socket, StreamCollection* streams)
: socket_(std::move(socket))
{
streams_ = streams; // keep a reference to the streamCollection
// retrieve endpoint ip
asio::ip::tcp::endpoint remote_ep = socket_.remote_endpoint();
asio::ip::address remote_ad = remote_ep.address();
this->ip_ = remote_ad.to_string();
}
void Stream::start()
{
streams_->join(shared_from_this());
readHeader();
}
void Stream::deliver(const chat_message& msg)
{
bool write_in_progress = !write_msgs_.empty();
write_msgs_.push_back(msg);
if (!write_in_progress)
{
write();
}
}
std::string Stream::getName()
{
return name_;
}
std::string Stream::getIP()
{
return ip_;
}
void Stream::RegisterListener(IStreamListener *l)
{
m_listeners.insert(l);
}
void Stream::UnregisterListener(IStreamListener *l)
{
std::set<IStreamListener *>::const_iterator iter = m_listeners.find(l);
if (iter != m_listeners.end())
{
m_listeners.erase(iter);
}
else {
std::cerr << "Could not unregister the specified listener object as it is not registered." << std::endl;
}
}
void Stream::readHeader()
{
auto self(shared_from_this());
asio::async_read(socket_,
asio::buffer(read_msg_.data(), chat_message::header_length),
[this, self](asio::error_code ec, std::size_t /*length*/)
{
if (!ec && read_msg_.decode_header())
{
readBody();
}
else if (ec == asio::error::eof || ec == asio::error::connection_reset)
{
std::for_each(m_listeners.begin(), m_listeners.end(), [&](IStreamListener *l) {l->onStreamDisconnecting(this->id()); });
streams_->die(shared_from_this());
}
else
{
std::cerr << "Exception: " << ec.message();
}
});
}
void Stream::readBody()
{
auto self(shared_from_this());
asio::async_read(socket_,
asio::buffer(read_msg_.body(), read_msg_.body_length()),
[this, self](asio::error_code ec, std::size_t /*length*/)
{
if (!ec)
{
// notify the listener (GUI) that a response has arrived and pass a reference to it
auto msg = std::make_shared<chat_message>(std::move(read_msg_));
std::for_each(m_listeners.begin(), m_listeners.end(), [&](IStreamListener *l) {l->onMessageReceived(msg); });
readHeader();
}
else
{
streams_->die(shared_from_this());
}
});
}
void Stream::write()
{
auto self(shared_from_this());
asio::async_write(socket_,
asio::buffer(write_msgs_.front().data(),
write_msgs_.front().length()),
[this, self](asio::error_code ec, std::size_t /*length*/)
{
if (!ec)
{
write_msgs_.pop_front();
if (!write_msgs_.empty())
{
write();
}
}
else
{
streams_->die(shared_from_this());
}
});
}
接口
class IStream
{
public:
/// Unique stream identifier
typedef void* TId;
virtual TId id() const
{
return (TId)(this);
}
virtual ~IStream() {}
virtual void deliver(const chat_message& msg) = 0;
virtual std::string getName() = 0;
virtual std::string getIP() = 0;
/// observer pattern
virtual void RegisterListener(IStreamListener *l) = 0;
virtual void UnregisterListener(IStreamListener *l) = 0;
};
class IStreamListener
{
public:
virtual void onStreamDisconnecting(IStream::TId streamId) = 0;
virtual void onMessageReceived(std::shared_ptr<chat_message> msg) = 0;
};
/*
streamCollection / service delegates
*/
class IStreamCollectionListener
{
public:
virtual void onStreamDied(IStream::TId streamId) = 0;
virtual void onStreamCreated(std::shared_ptr<IStream> stream) = 0;
};
StreamCollection 基本上是一组 IStream：
class StreamCollection
{
public:
void join(stream_ptr stream)
{
streams_.insert(stream);
std::for_each(m_listeners.begin(), m_listeners.end(), [&](IStreamCollectionListener *l) {l->onStreamCreated(stream); });
}
// more events and observer pattern inplementation
首先：代码按预期工作。
我的问题：
这是 ASIO 应该用于异步编程的方式吗？我特别不确定Service::send_message 方法和io_service.post 的使用。就我而言，它的目的是什么？当我只是调用 async_write 时它也确实有效，而没有将其包装在 io_service.post 调用中。
我是否遇到了这种方法的问题？
【问题讨论】：
标签： c++ boost boost-asio