Re: [Boost-users] Multiple async operations on a socket

Subject: Re: [Boost-users] Multiple async operations on a socket
From: Matheus Araújo Aguiar (matheus.pit_at_[hidden])
Date: 2009-09-17 10:02:33

On Thu, Sep 17, 2009 at 10:27 AM, Kyle Tarplee <Kyle.Tarplee_at_[hidden]>wrote:

> So it seems you can not have multiple outstanding async_read_some or
> async_write_some.  This makes since.
>

You might have multiple outstanding async requests. But in that case, you
must write code to assure consistence. For async_read, the completion
handlers may be called out of order, so you need to keep track about the
order of the requests (you could, for example, give a sequence number for
each async_read, and pass that number to the callback function). On the
other hand, for async_write, since it is divided in many async_write_some,
you must wait one operation complete before requesting another one. This
avoids your data being interleaved.
Read the links I posted in earlier message for further information.

Kindly,

>
> Now the thing that doesn't make since is that since a user could easily
> make such an error and the problem would be hard to track down (for instance
> it hasn't caused me a problem yet, just wasn't getting the warm fuzzy
> feeling about what I was doing) why does ASIO's socket not throw an error or
> behave more like the deadline_timer when one tries to create multiple async_
> operations.  The deadline_timer kindly cancels the async_wait() when you
> call expires_fron_now().  It seems like the socket could cancel the previous
> read/write by calling it's callback with an error like operation_aborted.
>
> Kyle
>
> On Sep 16, 2009, at 2:40 PM, Matheus Araújo Aguiar wrote:
>
>
> On Wed, Sep 16, 2009 at 4:39 PM, Igor R <boost.lists_at_[hidden]> wrote:
>
>> > I have a boost::asio::ip::tcp::socket that I want to write to.   Can I
>> have multiple outstanding async_write() requests for a single socket?
>>
>> asio::async_write() is a convenience function that calls
>> socket::async_write_some() multiple times - until all the data is
>> sent. This means that if you issue multiple asio::async_write's, the
>> data will be interleaved in most cases.
>> As for multiple async_write_some(), it will probably work on some
>> platforms... But note that async_write_some doesn't promise to send
>> all your data. So you can't "fire and forget" anyway.
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>
>
>
> I had the same doubt, and asked the same think some weeks ago. Here's what
> helped me figuring out what happens:
>  - http://archives.free.net.ph/message/20090821.085221.7ccd0f8a.pt-BR.html
>  -
> http://www.jetbyte.com/portfolio-showarticle.asp?articleId=44&catId=1&subcatId=2
>
> Regards,
> --
> Matheus Araújo Aguiar
> Computer Scientist
> matheus.pit_at_[hidden]
> <ATT00001..txt>
>
>
>
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>

-- 
Matheus Araújo Aguiar
Computer Scientist
matheus.pit_at_[hidden]