Re: [Boost-users] async_send handler problem

Subject: Re: [Boost-users] async_send handler problem
From: Alexander Carôt (Alexander_Carot_at_[hidden])
Date: 2013-12-17 10:54:40

>>Yes, I truly understand this but for some weired reason this doesn't work
>> at all. In my case I launch the run function in the constructor of the
>> main class right after the sender class had been instantiated:
>>
>> SJ::SJ(){
>>
>>   /// SENDER INIT
>>   dFC->mySender = new sender(this);
>>
>>
>>   boost::thread t =
>> boost::thread(boost::bind(&boost::asio::io_service::run,
>> &dFC->io_service));
>>   t.join();
>>
>>   // OR dFC->io_service.run();
>> }
>>
>>
>> In there anything wrong with this ?
>
>
>It seems that you call io_serivce::run() before any async operation
>was issued. In such a case, run() just exits immediately, as I
>explained in one of my previous comments. In order to avoid such a
>behavior,
>associate io_service::work object with this io_service:
>http://www.boost.org/doc/libs/1_55_0/doc/html/boost_asio/reference/io_serv
>ice.html

Allright - this helps but still issues (see below).

>In general, it's highly recommended to read the Asio documentation -
>all these issues are described there.

Yes, you can assume this but it seems the case is a little more complex
than it is the case with the default use cases:

This simple example works fine:

----------------------------
boost::asio::io_service io_service;

int i = 0;

void handle_send(const boost::system::error_code& error, std::size_t
bytes_transferred){
  i++;
  std::cout << "async_send_to return " << error << ": " <<
bytes_transferred << " transmitted " << i << std::endl;
}

int main(int argc, char *argv[]){
if(argc==3){

  boost::asio::io_service::work work(io_service);
  boost::thread t = boost::thread
(boost::bind(&boost::asio::io_service::run, &io_service));
  //t.join();

  boost::asio::ip::udp::socket socket(io_service);
  boost::asio::ip::udp::endpoint remote_endpoint;

  socket.open(boost::asio::ip::udp::v4());

  remote_endpoint = boost::asio::ip::udp::endpoint(
  boost::asio::ip::address::from_string(argv[1]),
boost::lexical_cast<int>(argv[2]));

  std::cout << "Send to " << remote_endpoint << std::endl;

  while (1)
  socket.async_send_to(boost::asio::buffer("message", 7), remote_endpoint,
                      boost::bind(&handle_send,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));

return 0;
}
-----------------------------

but with respect to my app this does not work:

I am specifying the io_service thread in my constructor.

SJ::SJ(){ 
  boost::asio::io_service::work work(dFC->io_service);
  boost::thread myThread(boost::bind(&boost::asio::io_service::run,
&dFC->io_service));
}

I have a handle in my custom SJ class:

void SJ::handleSend(const boost::system::error_code& error, std::size_t
bytes_transferred){
  cout << "SENT FROM HANDLER" << endl;
}

I have a send function:

void SJ::sendIt(){
  cout << "Send Funktion" << endl;
        
  dFC->s->async_send_to(boost::asio::buffer("message", 7),
remote_endpoint, 
  boost::bind(&handleSender, boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}

The send function is called from an *non-class-member* callback thread
(my->sj->sendIt()):

static int audioCallback( void *data ){
  SJ::callbackdata *my;
  my = (SJ::callbackdata *) data;

  my->sj->sendIt();
}

Not that everything works fine when I call the send function from within
my SJ-class but when I call the send function from the external callback
thread the handler is not triggering anymore.

Does this help to clarify what (or where) my problem is ?

Thanks again

Alex