fds
    An array of pollfd structures, one for each file descriptor of
    interest. Each pollfd structure includes the following members:
    int fd           The file descriptor
    int events       The requested conditions
    int revents      The reported conditions
 nfds
    The number of pollfd structures in the fds array.
 timeout
    The maximum length of time (in milliseconds) to wait for one of
    the specified events to occur.