When using blocking the way of receiving data have a chance to receive less than data would happen, peripherals in a fixed cycle to send data, use the select at the beginning, there are always return zero chance happen, then use epoll, countless according to judgement may appear same situation, calls epoll_wait, waitNum=epoll_wait (epid, events, 1024, 1); Program would have been parked in the here, ask bosses help analysis of a wave of what went wrong