Hello All, I'm new in boost asio. I'm trying to adapt this library to my existent network application. There is a problem with current application's architecture. I see no way to pass some parameter to the completion routine from the io_service::run calling thread. Below brief application description. Hope this will help: 1. It is *low-latency* network application 2. Application processes incoming multicast UDP messages. 3. Number of multicast groups/ports is *unlimited*. Technical details: 1. Application encapsulates udp::sockets subscribed to multicast group 2. udp::socket::async_receive method used to receive data 3. io_service::run is used in the thread pool to call socket's complete routine. 4. Every thread of the pool encapsulates some object for messages processing. I need to pass reference to this object to the socket::async_receive complete routine to complete message processing. This object allocates a lot of memory and I cannot create it for every socket. It is possible to create but there is no sense. It is very important to avoid thread_local_storages and null_buffers to make application as simple as possible without performance gaps. I believe it is possible because POSIX and Windows I/O allow it. Please help with advise. Thanks. Dima