Thank you for your help but it didn't change anything. After few hours working on this problem, i've fix it: In a new VS2010 project, with the same source code, this code works without any error in async_accept callback. Finally, i find out that it didn't work because i was using pragma lib in one of my file for managing windows services: #pragma comment (lib, "advapi32.lib") #pragma comment (lib, "user32.lib") When I removed this file, error disappears. Then, I put theses lib in project's configuration instead of using pragma and everything works! Although I don't understand the problem, it's now working. Thank you for your help Cyprien DIOT ----- Mail original ----- De: "Igor R" <boost.lists@gmail.com> À: boost-users@lists.boost.org Envoyé: Jeudi 10 Mars 2011 15:58:17 Objet: Re: [Boost-users] [ASIO] async_accept : Error m_val 1.

What is "already open" ? _client ? It has just been allocated before calling async_accept. _io is properly initialized.

If this error is about acceptor, how can I use it with async_accept ? I've seen http://www.boost.org/doc/libs/1_37_0/doc/html/boost_asio/reference/basic_soc... but i don't see any line where the listen port is set to acceptor.

Like Viatcheslav mentioned, set reuse_address option: http://think-async.com/Asio/boost_asio_1_5_2/doc/html/boost_asio/reference/s... _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users