Re: [Boost-users] Why do socket::receive() and socket::async_receive() have different return types?

Subject: Re: [Boost-users] Why do socket::receive() and socket::async_receive() have different return types?
From: Geert Martin Ijewski (gm.ijewski_at_[hidden])
Date: 2018-06-14 15:10:47

Hello,

Am 14.06.2018 um 16:04 schrieb Álvaro Cebrián Juan via Boost-users:
> From the documentation I can see that socket::receive()
> <https://www.boost.org/doc/libs/1_58_0/doc/html/boost_asio/reference/basic_datagram_socket/receive.html>
> returns a variable of type "std::size_t", while the asynchronous version
> socket::async_receive()
> <https://www.boost.org/doc/libs/1_58_0/doc/html/boost_asio/reference/basic_datagram_socket/async_receive.html>
> returns "void". 

`socket::receive()` returns how much has been received and is similar to
`recv()`. `socket::async_receive()` does not actually receive stuff --
it only tells your `asio::io_service` that as *it* receives something it
shall pass that data on to your callback.

Because `socket::async_receive()` is asynchronous (it only registers the
socket <-> callback) and doesn't receive anything it can't return any
meaningful size.

This is one of the concepts of asynchronous development, I think
refreshing your knowledge about that would be benefital.

>This is also true for socket::send()
> <https://www.boost.org/doc/libs/1_58_0/doc/html/boost_asio/reference/basic_datagram_socket/send.html>
> and socket::async_send()
> <https://www.boost.org/doc/libs/1_58_0/doc/html/boost_asio/reference/basic_datagram_socket/async_send.html>.
> I was expecting that they would have the same return types, so there
> might be a good reason behind.
> 
> I would be grateful if someone can shed some light on this.
> 
> Thank you.
> 
> Álvaro
> 
> 
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