1.

While the usage of epoll when employed as a level-triggered interface
       does have the same semantics as poll(2)

int addfd(int epollfd,int fd, bool enable_et)
{
    struct epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN;
    if(enable_et)
    {
        
 
event.events |= EPOLLET;
    }
    epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&event);
    setnonblocking(fd);
}

http://www.man7.org/linux/man-pages/man7/epoll.7.html

http://www.cnblogs.com/charlesblc/p/5521086.html

https://github.com/Tianxintong/LT_ET