Htykuut

been trying to solve this problem i am facing concerning the io_service object. The code in question in so:

    void connect_handler(const error_code &ec,iterator iterator){

        cout<<"Connect handler"<<endl;

    }



    void resolver_handler(const error_code &ec,iterator iterator,boost::asio::io_service &io){

        cout<<"Resolver handler..."<<endl;

        boost::asio::ip::tcp::socket socket(io);

        boost::asio::async_connect(socket,iterator,&connect_handler);

    }



    int main(){

        boost::asio::io_service io;

        resolver resolver(io);

        resolver::query query("example.com","http");

        resolver.async_resolve(query,boost::bind(resolver_handler,boost::asio::placeholders::error,boost::asio::placeholders::iterator,boost::ref(io)));

        cout<<io.run()<<endl;



        return 0;

    }

Tried the same thing in another simple example, with everything running as intended:

void printTwo(const error_code& ec,boost::asio::deadline_timer &timer,boost::asio::io_service &io){

    cout<<"print two"<<endl;

}



void printOne(const error_code& ec,boost::asio::deadline_timer &timer,boost::asio::io_service &io){

    cout<<"print one"<<endl;

    timer.async_wait(boost::bind(printTwo,boost::asio::placeholders::error,boost::ref(timer),boost::ref(io)));

}



int main(int argc, char** argv) {

    boost::asio::io_service io;

    boost::asio::deadline_timer timer(io,boost::posix_time::seconds(3));

    timer.async_wait(boost::bind(printOne,boost::asio::placeholders::error,boost::ref(timer),boost::ref(io)));

    cout<<io.run()<<endl;

    return 0;

}

My assumptions is that the service object blocks until all work is done; also the thread that calls the run function is the thread that the handler functions are called from. So, why does the second block of code work as intended, but not the first? thanks in advance.

io.run() in your program will return as soon as the io_service thinks it's done with the work it has to do. This could happen between operations or maybe when the last async callback is called (I'm not completely sure).

Use a work object to inform the io_service to keep running, and when you reset that work object, the io_service's run() call should return once it's done executing any pending operations.

The basic use is something like this:

boost::asio::io_service io_service;

boost::asio::io_service::work work(io_service);

// ...

io_service.run(); // Blocks here

And usually in another thread or maybe in one of the async callbacks, you do this:

work.reset();

And some time later, run() will return.