The implementation of do_one in win_iocp_io_service.hpp causes the waiting thread to wakeup every second, but I can't see any reason for doing so. The wakeup causes unnecessary context switches, which could have an impact on a busy machine, so what is the reasoning behind them? Thanks. Jim ________________________________________________________________________ This e-mail, and any attachment, is confidential. If you have received it in error, do not use or disclose the information in any way, notify me immediately, and please delete it from your system. ________________________________________________________________________