boost::asio when should I use socket::async_send instead of the free function async_write?

socket::async_send() is a composed method which is implemented in termos of zero or more calls to socket::async_write_some(). However, as the documentation describes:

The send operation may n开发者_Go百科ot transmit all of the data to the peer.

So, when do I need such a behavior?

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When you are bursting info on the socket and part of the info is disposable.