asio-users

[asio-users] usage of async_receive_from (in udp broadcast application)

[Bart De L. <bar...@pa...>]

Hello

I recently wrote an application that broadcasts a message on my network, and waits for the responses coming in.
Sending the udp broadcast message goes OK, the machines that listen on the network send the responds alright, but i'm stuck getting the responses using "async_receive_from".

Here is some code:

udp::resolver resolver(io_service);
udp::resolver::query query(udp::v4(), "255.255.255.255", "16543");
udp::endpoint receiver_endpoint = *resolver.resolve(query);

// Create and open the socket
socket_ = new udp::socket(io_service);
socket_->open(udp::v4());

// Allow broadcasting
asio::socket_base::broadcast option(true);
socket_->set_option(option);

// Send out our message
boost::array<char, 1> send_buf  = { 0 };
socket_->send_to(boost::asio::buffer(send_buf), receiver_endpoint);

// read the responses in function 'Receive'
socket_->async_receive_from(boost::asio::buffer(recv_buffer_), sender_endpoint_, Receive);
// But io_service never calls Receive. (but calling "socket_->receive_from" does get me the responds)

So here is the question: how do i correctly use async_receive_from?
(all variables are defined in the .h (like io_service, socket_, etc ))

Thanks for looking into this
Bart

Re: [asio-users] usage of async_receive_from (in udp broadcast application)

[Christopher K. <ch...@ko...>]

On Tue, 07 Jul 2009 19:11 +0200, "Bart De Lathouwer"
<bar...@pa...> wrote:
> Hello
> 
> I recently wrote an application that broadcasts a message on my network,
> and waits for the responses coming in.
> Sending the udp broadcast message goes OK, the machines that listen on
> the network send the responds alright, but i'm stuck getting the
> responses using "async_receive_from".
> 
> Here is some code:
> 
> udp::resolver resolver(io_service);
> udp::resolver::query query(udp::v4(), "255.255.255.255", "16543");
> udp::endpoint receiver_endpoint = *resolver.resolve(query);
> 
> // Create and open the socket
> socket_ = new udp::socket(io_service);
> socket_->open(udp::v4());
> 
> // Allow broadcasting
> asio::socket_base::broadcast option(true);
> socket_->set_option(option);
> 
> // Send out our message
> boost::array<char, 1> send_buf  = { 0 };
> socket_->send_to(boost::asio::buffer(send_buf), receiver_endpoint);
> 
> // read the responses in function 'Receive'
> socket_->async_receive_from(boost::asio::buffer(recv_buffer_),
> sender_endpoint_, Receive);
> // But io_service never calls Receive. (but calling
> "socket_->receive_from" does get me the responds)
> 
> So here is the question: how do i correctly use async_receive_from?
> (all variables are defined in the .h (like io_service, socket_, etc ))

You didn't show it, so can you please confirm at which point you call
io_service.run()? Thanks.

Cheers,
Chris

Re: [asio-users] usage of async_receive_from (in udp broadcastapplication)

[Roger A. <rog...@wa...>]

I have a pretty basic question, but it isn't obvious from your code, so:

 

You are calling io_service::run somewhere, right?

 

If not, your completion handler for the call to async_receive_from (i.e.
Receive) will never get called. If you are calling it (perhaps in a
different thread) then you also need to be careful that it has not
already exited (due to lack of work) before the call to
async_receive_from

 

The asio examples are a very good place to start for an illustration of
correct usage.

 

From: Bart De Lathouwer [mailto:bar...@pa...] 
Sent: Wednesday, 8 July 2009 7:12 AM
To: asi...@li...
Subject: [asio-users] usage of async_receive_from (in udp
broadcastapplication)

 

Hello

 

I recently wrote an application that broadcasts a message on my network,
and waits for the responses coming in.

Sending the udp broadcast message goes OK, the machines that listen on
the network send the responds alright, but i'm stuck getting the
responses using "async_receive_from".

 

Here is some code:

 

udp::resolver resolver(io_service);
udp::resolver::query query(udp::v4(), "255.255.255.255", "16543");
udp::endpoint receiver_endpoint = *resolver.resolve(query);

 

// Create and open the socket
socket_ = new udp::socket(io_service);
socket_->open(udp::v4());

 

// Allow broadcasting
asio::socket_base::broadcast option(true);
socket_->set_option(option);

 

// Send out our message
boost::array<char, 1> send_buf  = { 0 };
socket_->send_to(boost::asio::buffer(send_buf), receiver_endpoint);

 

// read the responses in function 'Receive'

socket_->async_receive_from(boost::asio::buffer(recv_buffer_),
sender_endpoint_, Receive);

// But io_service never calls Receive. (but calling
"socket_->receive_from" does get me the responds)

So here is the question: how do i correctly use async_receive_from?

(all variables are defined in the .h (like io_service, socket_, etc ))

 

Thanks for looking into this

Bart


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Re: [asio-users] usage of async_receive_from (in udpbroadcastapplication)

[Bart De L. <bar...@pa...>]

Hello Christopher, Roger,

I simply forgot to call io_service.run()
(instant sunburn :-)

The most basic acton i forgot to do. My bad.
I knew i was missing something....

Thanks for pointing it out
Bart

  ----- Original Message ----- 
  From: Roger Austin 
  To: asi...@li... 
  Sent: Wednesday, July 08, 2009 5:39 AM
  Subject: Re: [asio-users] usage of async_receive_from (in udpbroadcastapplication)


  I have a pretty basic question, but it isn't obvious from your code, so:

   

  You are calling io_service::run somewhere, right?

   

  If not, your completion handler for the call to async_receive_from (i.e. Receive) will never get called. If you are calling it (perhaps in a different thread) then you also need to be careful that it has not already exited (due to lack of work) before the call to async_receive_from

   

  The asio examples are a very good place to start for an illustration of correct usage.

   

  From: Bart De Lathouwer [mailto:bar...@pa...] 
  Sent: Wednesday, 8 July 2009 7:12 AM
  To: asi...@li...
  Subject: [asio-users] usage of async_receive_from (in udp broadcastapplication)

   

  Hello

   

  I recently wrote an application that broadcasts a message on my network, and waits for the responses coming in.

  Sending the udp broadcast message goes OK, the machines that listen on the network send the responds alright, but i'm stuck getting the responses using "async_receive_from".

   

  Here is some code:

   

  udp::resolver resolver(io_service);
  udp::resolver::query query(udp::v4(), "255.255.255.255", "16543");
  udp::endpoint receiver_endpoint = *resolver.resolve(query);

   

  // Create and open the socket
  socket_ = new udp::socket(io_service);
  socket_->open(udp::v4());

   

  // Allow broadcasting
  asio::socket_base::broadcast option(true);
  socket_->set_option(option);

   

  // Send out our message
  boost::array<char, 1> send_buf  = { 0 };
  socket_->send_to(boost::asio::buffer(send_buf), receiver_endpoint);

   

  // read the responses in function 'Receive'

  socket_->async_receive_from(boost::asio::buffer(recv_buffer_), sender_endpoint_, Receive);

  // But io_service never calls Receive. (but calling "socket_->receive_from" does get me the responds)

  So here is the question: how do i correctly use async_receive_from?

  (all variables are defined in the .h (like io_service, socket_, etc ))

   

  Thanks for looking into this

  Bart



  The information contained in this e-mail is likely to be confidential and may be legally privileged. It is intended only for the addressee. If you have received this message in error please notify the sender immediately at the above address. The disclosure, copying or distribution of this message or its contents without the prior approval of Wallingford Software is strictly prohibited. Wallingford Software is not liable for unauthorised disclosures nor for subsequent actions or omissions in reliance upon them.
  Registered in the UK, Company no: 02288719 Wallingford Software Limited, Howbery Park, Wallingford, Oxfordshire, OX10 8BA





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