Por Una Cabeza

—instead of having to write all this:

/* Start with fd just returned by socket(), blocking, SOCK_STREAM... */
if ( connect (fd, &name, namelen) == -1 )
  {
    struct pollfd unix_really_sucks;
    int some_more_junk;
    socklen_t yet_more_useless_junk;

    if ( errno != EINTR /* && errno != EINPROGRESS */ )
      {
        perror ("connect");
        exit (EXIT_FAILURE);
      }
    unix_really_sucks.fd = fd;
    unix_really_sucks.events = POLLOUT;
    while ( poll (&unix_really_sucks, 1, -1) == -1 )
      if ( errno != EINTR )
        {
          perror ("poll");
          exit (EXIT_FAILURE);
        }
    yet_more_useless_junk = sizeof(some_more_junk);
    if ( getsockopt (fd, SOL_SOCKET, SO_ERROR,
                     &some_more_junk,
                     &yet_more_useless_junk) == -1 )
      {
        perror ("getsockopt");
        exit (EXIT_FAILURE);
      }
    if ( some_more_junk != 0 )
      {
        fprintf (stderr, "connect: %s\n",
                 strerror (some_more_junk));
        exit (EXIT_FAILURE);
      }
  }
/* At this point, fd is connected. */

see it:

http://www.madore.org/~david/computers/connect-intr.html