How to websocket in grails5 - grails

Question

I want a grails application in which server sends some message at a fixed interval.
I have tried using spring-websocket plugin in grails, server and client are able to connect but that doesn't fullfill my requirement. i.e., I want, server sends some message at a fixed interval.
This is the server-side code :
package test
import org.springframework.messaging.handler.annotation.MessageMapping
import org.springframework.messaging.handler.annotation.SendTo
class ExampleController {
def index() { }
// server
#MessageMapping("/hello")
#SendTo("/topic/hello")
protected String hello(String world) {
List<String> list = new ArrayList<>();
BufferedReader file = new BufferedReader(new FileReader("src/main/resources/dummyLog.txt"));
file.eachLine {line ->
list.add(line)
}
int idx = (int)(Math.random() * list.size());
println idx;
return list.get(idx);
}
}
And this is the client-side code :
<script type="text/javascript">
document.addEventListener('DOMContentLoaded', () => {
var socket = new SockJS("${createLink(uri: '/stomp')}");
var client = webstomp.over(socket);
client.connect({}, function() {
client.subscribe("/topic/hello", (message) => {
document.getElementById('helloDiv').append(message.body);
});
});
document.getElementById('helloButton').addEventListener('click', () => {
client.send("/app/hello", JSON.stringify("world"));
});
});
</script>
Thanks.