Hi, I am using the async_tcp_echo_server.cpphttp://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/echo/async_...sample code to understand asio. when I am tracing code in visual studio, it doeasn't let me put a breakpoint inside start() function in session class. Will it be run in another thread? is that the reason for not being able to put a breakpoint? Though it seems I can put breakpints for other codes that run in other threads... Why can I not put here? I tried to break at the point calling this function and step into from there. it jumps to async_receive(...) function in win_iocp_socket_service.hpp file. Could someone help me understand what is going on, or give me some pointers about how to trace such code? TIA, Ozgur PS: here is the related code: class session { //... //this is the part I can not put breakpoint. void start() { socket_.async_read_some(boost::asio::buffer(data_, max_length), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } Best regards, Ozgur (Oscar) Ozturk www.DrOzgur.com +1 (614) 805-4370