Re: [asio-users] basic_stream_socket::async_connect -- non-blockingconnect vs async connect

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

Chauhan, Vikas wrote:
> Hello all,
> 
> I think I have found the reason for this.
> 
> Actually, I had the following sequence of calls earlier :
> 1. tcp::socket::async_connect(peer_endpoint,connect_handler ).
> 2. io_service::run() 
> 
> Logically, step 2 should precede step 1, but I could not do that as
> io_service::run() was failing as there was nothing registered to it. 

There should be no requirement to perform the run first. Starting the 
async_connect gives the io_service "work" to do in any case.

> Now, I have created an instance of  "boost::asio::io_service::work " in
> the beginning of program. It helps the io_service to queue any aync
> calls.
> Hence now the sequence of calls is :
> 1. boost::asio::io_service::work(ioservice) 
> 2. io_service::run() 
> 3. tcp::socket::async_connect(peer_endpoint,connect_handler ).
> 
> Thanks to those who may have tried to find out reasons for the problem.

I'm a bit confused about what your original problem was now :) An 
async_connect operation should take the same length of time to complete 
as a blocking connect operation. E.g. if a connect takes 20 seconds then 
an async_connect should also take 20 seconds.

However it now sounds like you're talking about when the completion 
handler itself is called, and that is only allowed to occur from within 
a call to io_service::run() (or run_one, poll or poll_one). You can 
start an async_connect and then not call io_service::run() straight 
away, in which case your handler won't be called until you do.

Cheers,
Chris