Allows you to poll or check a group of sockets for I/O activity.
    This function indicates which sockets are ready to be read or
    written, or which sockets have an exception pending.
    Format
      #include  <time.h>
      int select  ( int nfds, int *readfds, int *writefds,
                  int *execptfds, struct timeval *timeout );
                  (_DECC_V4_SOURCE)
      int select  ( int nfds, fd_set *readfds, fd_set *writefds,
                  int *execptfds, struct timeval *timeout );
                  (not_DECC_V4_SOURCE)