Christopher Kohlhoff wrote:

What OS are you using? Is the session's work CPU bound?

I'm on Windows XP, sry but I can't understand what you mean with the second question... Just take your sample in "server.cpp": I need to be able to change the code (in the session or server object, dunno where...) so that the server is always free to accept (and process) a new connections even if there are one or more active sessions taking a very long time to generate and send theirs response. For example: void Session::handle_read(const asio::error_code& err, size_t length) { --op_count_; if (!err) { read_data_length_ = length; ++unsent_count_; if (unsent_count_ == 1) { very_very_long_operation(); // Process the client request op_count_ += 2; std::swap(read_data_, write_data_); async_write(socket_, buffer(write_data_, read_data_length_), strand_.wrap( boost::bind(&session::handle_write, this, placeholders::error))); socket_.async_read_some(buffer(read_data_, block_size_), strand_.wrap( boost::bind(&session::handle_read, this, placeholders::error, placeholders::bytes_transferred))); } } if (op_count_ == 0) io_service_.post(boost::bind(&session::destroy, this)); } Session::very_very_long_operation() takes a lot of time I need in the meanwhile to be able in the server to accept new connections, how can I do that? I tried calling ios.run() from multiple threads as the documentation said but the server is always locked until the session's operation is completed... P.S.: be patient plz my english is not very good