The proper way to repair the broken pipe is to open the floor enough to acess the closest fitting. then either extract the broken nipple or cut the fitting out and adapt to plastic from there. A fernco is Not code approved for this. if anything a no hub band could be used. I am a licensed high end service plumber for over 15 years alot of the tips on this site come from plumbing butchers. If the pipe broke off you are miles ahead to do it right and be done with it.