可参考链接select函数详解-CSDN博客

select读模板：

    int            retval;
    fd_set         rfds;
    struct timeval tv;

    FD_ZERO(&rfds);
    FD_SET(m_fd, &rfds);
    tv.tv_sec  = s32MilliSec / 1000;                      // s32millisec 为5000时，为五秒
    tv.tv_usec = (s32MilliSec % 1000) * 1000;

    retval = select(m_fd + 1, &rfds, NULL, NULL, &tv);
    if (retval == -1) {
        perror("select()");
    } else if (retval && FD_ISSET(m_fd, &rfds)) {
        int32 s32ReadLen = SafeRead(m_fd, pu8Buf, s32BufLen);
    if (s32ReadLen <= 0) {
            XSleep(100);
            return -1;
        } else {
            return s32ReadLen;
        }
    } else  //time out
    {
    }