Java - how sockets how can I receive data without constantly pinging

Question

Okay, so I have an apache server that has text/data that I want to sendoff to a Java client. The issue is that the data will change often, and I don't want the client to constantly do a read on the server, because obviously I don't want a constant ping. I know that I can make a client socket but that requires my users to port forward to access the server, which isn't going to work for my users.

What I've found online is UDP punching may work or NAT Transfer, but I cant find any examples for how to do it in Java.

If you have any questions please feel free to comment :)

I havn't found anything that will allow the server to respond randomly to the client. Because its an apache webserver I don't think you can do events.? — DrBrad, Apr 14 '17 at 20:38

score 1 · Accepted Answer · answered Apr 14 '17 at 20:45

1

You could Recieve Server-Sent Event notifications, in which the server send the data, using PHP and JS as an example:

var source = new EventSource("demo_sse.php");
source.onmessage = function(event) {
    document.getElementById("result").innerHTML += event.data + "<br>";
};

PHP:

<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');

$time = date('r');
echo "data: The server time is: {$time}\n\n";
flush();
?>

answered Apr 14 '17 at 20:45

Ricardo Ortega Magaña

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Thank you, do you know how I could do an onmessage with Java as well? – DrBrad Apr 14 '17 at 20:47
Check this question: http://stackoverflow.com/questions/31768349/how-does-server-sent-events-work – Ricardo Ortega Magaña Apr 14 '17 at 20:50
What you sent works well in java but thats assuming that I want a server, is there a way to get server events as a client in Java? – DrBrad Apr 17 '17 at 20:20
i dont understand what you want to achieve. Please elaborate. – Ricardo Ortega Magaña Apr 17 '17 at 20:48
So I checked out the java servlet for a while and used the doGet, but it doesn't seem to allow me to receive server-sent events. So in other words how would I be able to do what you did with javascript in java? – DrBrad Apr 17 '17 at 20:54
Check this answer: http://stackoverflow.com/questions/10878243/sse-and-servlet-3-0 it have an example of a Java Servlet aquiring the data stream. – Ricardo Ortega Magaña Apr 18 '17 at 01:06

Java - how sockets how can I receive data without constantly pinging

1 Answers1