https://rifco.ru/blog/2014/05/22/comet-push-%d1%81%d0%b5%d1%80%d0%b2%d0%b5%d1%80-%d0%be%d1%82%d0%ba%d0%bb%d1%8e%d1%87%d0%b0%d0%b5%d0%bc-%d0%bb%d0%be%d0%b3%d0%b8/