Fun topic this is. Well a friend of mine went to jail for like 3 months (he was innocent and went home at trial) and he had some fun stories from there. This happened in Germany by the way. He really likes sports betting and made good money being some kind of bookie for a short while. He told me he got the latest odds from the TV and accepted bets, for cigarettes, coffee or anything other that has some sort of worth. He also told me they were playing poker a lot, for the money they were earning for their shitty jail jobs.
Anyway, gambling inside was just as bad as outside he said. Emotions sometimes boil over and this can end badly.