I have a web interface through which I can perform/apply actions on backend systems like Hadoop. I am trying to code a functionality which allows me to track the status of the server. Basically to see if the server/service is up or down. I need to do this every 2 minutes. So should I go with a Websocket or a SSE(Server Sent Event) for this..I have written this code to perform this. However the moment I code for checking the status every 2 minutes. It becomes a blocking call and I am unable to perform any other functionality of the Web UI
Following is the Code
import java.io.*;
import java.net.*;
import java.util.concurrent.TimeUnit;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
@ServerEndpoint("/echo")
public class Websocket {
@OnOpen
public void onOpen(Session session){
System.out.println(session.getId() + " has opened a connection");
try {
session.getBasicRemote().sendText("Connection Established");
} catch (IOException ex) {
ex.printStackTrace();
}
}
@OnMessage
public void onMessage(String message, Session session){
System.out.println("Message from " + session.getId() + ": " + message);
try {
Integer a;
a=message.length();
if (a==4)
{
onping(session);
}
else
{
session.getBasicRemote().sendText(message);
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
public void onping(Session session) throws IOException
{ if (session.isOpen())
{
session.getBasicRemote().sendText("In PING");
String ip = "200.168.100.46";
InetAddress inet = InetAddress.getByName(ip);
if(inet.isReachable(50075))
{
session.getBasicRemote().sendText("Alive");
}
}
else
{
System.out.println("Error");
}
}
@OnClose
public void onClose(Session session){
System.out.println("Session " +session.getId()+" has ended");
}
}
And the Client Side Code is
<!DOCTYPE html>
<html>
<head>
<title>Websocket</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
</head>
<body>
<div>
<input type="text" id="messageinput"/>
</div>
<div>
<button type="button" onclick="openSocket();" >Open</button>
<button type="button" onclick="closeSocket();" >Close</button>
<button type="button" onclick="pingSocket();" >Ping</button>
</div>
<!-- Server responses get written here -->
<div id="messages"></div>
<!-- Script to utilise the WebSocket -->
<script type="text/javascript">
var webSocket;
var messages = document.getElementById("messages");
function openSocket(){
// Ensures only one connection is open at a time
if(webSocket !== undefined && webSocket.readyState !== WebSocket.CLOSED){
writeResponse("WebSocket is already opened.");
return;
}
// Create a new instance of the websocket
webSocket = new WebSocket("ws://localhost:8080/Websocket/echo");
/**
* Binds functions to the listeners for the websocket.
*/
webSocket.onopen = function(event){
// For reasons I can't determine, onopen gets called twice
// and the first time event.data is undefined.
// Leave a comment if you know the answer.
if(event.data === undefined)
return;
writeResponse(event.data);
};
webSocket.onmessage = function(event){
writeResponse(event.data);
};
webSocket.onclose = function(event){
writeResponse("Connection closed");
};
}
/**
* Sends the value of the text input to the server
*/
function send(){
var text = document.getElementById("messageinput").value;
webSocket.send(text);
}
function pingSocket(){
var text = document.getElementById("messageinput").value;
webSocket.send("PING");
}
function closeSocket(){
var text = document.getElementById("messageinput").value;
webSocket.send(text);
webSocket.close();
}
function writeResponse(text){
messages.innerHTML += "<br/>" + text;
}
</script>
</body>
</html>
So can you let me know what am i doing wrong?
Thanks
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