rails server not response after idle a while(1 or 2 hours)

I started rails server with puma webserver.(Centos 7) simple command rails s -b 0.0.0.0 . It is working great in working hours these day. But next day can't call rails server.(but can call rails server 1 times and like cache . And then no more access.) It seen like request to server and don't get response and waiting server response. After check rails log, only have one update log for today. (when I get response 1st time.)