Running server in C9-google cloud, but couldn't see iit n C9 "Preview"


[info] Running com.example.WebServerHttpApp
Press RETURN to stop…
[INFO] [06/21/2017 16:13:37.681] [] [] Server online at http://localhost:8080/

$ curl http://localhost:8080
Server up and running


does your server listen on localhost or, only servers listening on are proxied by preview.
You can use preview>show active servers menu item, or netstat -tulpn terminal command, to check that.