Related
Lately I've been researching about technologies with which I could develop a simple chat using PHP and AJAX. Since I prefer not to install any software, I've decided to use SSE (Server Sent Events) instead of websockets.
This method allows the client who calls the php file to receive data without making a request, which is what I want, but the problem comes with the fact that every new client connecting executes the same php file again, instead of accessing the one that is already running and getting the same responses than every other client.
This means that if multiple clients calling the php file to receive data, the server will overload at some point. Knowing that, would it be possible to make every client receive the data coming only from one php executing file?
Here is what is going on:
This is okay, but as you can see, I end up having the same file executing two times, one for every client.
Here is what I want to do:
As you can see here, there is only one php file sending data, but multiple clients are receiving it.
How is this possible?
myFile.php
<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
$number = 0;
while(true){
echo "data: $number ";
echo "\n\n";
$number++;
sleep(1);
#ob_flush();
flush();
}
?>
client.html
<!DOCTYPE html>
<html>
<body>
<h1>Getting server updates</h1>
<div id="result"></div>
<script>
if(typeof(EventSource) !== "undefined") {
var source = new EventSource("myFile.php");
source.onmessage = function(event) {
document.getElementById("result").innerHTML += event.data + " ";
};
} else {
document.getElementById("result").innerHTML = "Your browser doesn´t support SSE (server-sent events)";
}
</script>
</body>
</html>
Thanks in advance.
Okay so I've finally solved the question. The answer is NO, multiple clients can't receive data from one single executing SSE script, since that would mean a huge security vulnerability for any client that uses it.
Apart from that, SSE is design to lock the session of the client who is opening the scrip until it ends or closes. This way, if some session parameter changes during the execution of the SSE, it won't read it. The only way to change session parameters during the execution, is by using the session_commit() function to commit those session changes.
This also means that if the session is locked, you the client won't be able to receive any other http response until the SSE script closes. Every response will stay on pending status until that happens.
This applies to ajax, whil also works with http asyn requests. At the time the SSE lock the session, the client will stop receiving ajax responses until the SSE script stops, or until the SSE script uses the session_commint() function.
This post helped me to understand how it works.
I'm trying to display the results while PHP script is running, as example.. a really long loop, i want it to echo the results while the page is loading, I searched really a lot through this and i couldn't find the good answer, After googling i found people saying use ob_flush from this question .. but it didn't work, as well as enabling the implicit_flush from php.ini , still didn't work
it only loads when the process is finished, i tried to run a for loop like this
ob_start();
for($i=0; $i<500; $i++){
echo "hm\n";
ob_flush();
}
ob_end_flush();
and still, didn't work.. it shows them all at once
My last guess now is that it needs more PHP configurations to enable/disable some stuff,
or.. it could also be apache2 configurations ?
What are the config settings that are related to this ? settings that needs to be disabled/enabled through Apache or PHP configurations ..
P.S. : I'm sure its possible to be done using PHP alone, I saw it done on GoDaddy hosting and saw it on several websites, of them http://www.checker.freeproxy.ru/checker/index.php .. if you try to submit it will show the results normally without using ajax, the website uses PHP and Apache, there's a mystery secret behind this
I used this way from this answer
while(1) {
echo "should display these lines on browser while in infinite loop.<br>";
flush();
}
or using the for loop, they both work fine, and it to make it more accurate i use ob_flush() with flush()
for($i=0; $i<5000; $i++) {
echo "should display these lines on browser while in infinite loop.<br>";
usleep(30000);
ob_flush();
flush();
}
they both work fine without ajax
Check my post here: Show progress bar in php while loop
It has some sample code as well, and covers pretty much everything you need.
PS: It can't be done with PHP alone, you need to do this with AJAX + PHP (client + server side coding). This is because the response is sent to the browser only after the file is fully interpreted.
You can't do this with PHP. PHP is run server side so it executes before the HTTP response is sent back to the browser.
You would need to use AJAX to achieve this.
You may also look at websockets to achieve this kind of thing.
You could also cheat and load all the data into a hidden list, and then use javascript to show the list items one by one after the page has loaded. :)
As mentioned above, Ajax would be the best method.
You'll need 3 files, a html file or php file that heads the job, a javascript file with your ajax in it and the php file running your script, here's an example of how you could do this. The rest is up to you if you need it tweaking for whatever you are trying to do, but it should give a sequential redout if you break up your php accordingly.
go.hml:
<html>
<head>
<title>Insert Title Here</title>
<script src="ajax_example.js" language="javascript"></script>
</head>
<body>
<form action="javascript:insert()" method="post">
<input type="text" name="limit" value="" id="limit"/>
<input type="submit" name="Submit" value="Go"/>
</form>
<div id="text_response"></div>
</body>
</html>
ajax_example.js:
// make script work for internet explorer too
function createObject(){
var request_type;
var browser = navigator.appName;
if(browser == 'Microsoft Internet Explorer'){
request_type = new ActiveXObject('Microsoft.XMLHTTP');
}else{
request_type = new XMLHttpRequest();
}
return request_type;
}
var http = createObject();
var response = '';
var current = 0;
var limit = 0;
function insert(){
current = 0;
// write to the document
response = 'Hang on...';
document.getElementById('text_response').innerHTML = response;
// set the limit and run the loop script
limit = encodeURI(document.getElementById('limit').value);
limit++;
loop_file(current);
}
function loop_file(i) {
// open the php file you wish to run, the 'hm' and 'rand' are optional, obviously
http.open('get', 'file.php?hm='+i+'&rand='+Math.random());
// run the insertReply function
http.onreadystatechange = insertReply;
http.send(null);
}
function insertReply(){
if(http.readyState == 4){
response = response+'<br />'+http.responseText;
document.getElementById('text_response').innerHTML = response;
current++;
// this runs like a pseudo for loop and will loop until it reaches the 'limit'
if(current < limit){
loop_file(current);
}else if(current == limit){
//create end script here
}
}
}
file.php
<?php
echo isset($_GET['hm']) ? $_GET['hm'] . " - hm\n" : "hm\n";
?>
I'm looking to implement a chat room using PHP/Javascript (Jquery) with both group chat and private chat features.
The problem is how to continually update the interface in a natural way and possibly also how to show 'X is typing..' messages in private chat.
The obvious way seems to be that every X seconds/milliseconds the javascript pings the server and fetches a list of new messages between the last ping and now. However, this can make the interface seem a bit unnatural, if suddenly the chat room is flooded with 5 messages. I would rather each message appear as it is typed.
Is there a way for javascript to maintain a continuous connection to the server, the server pushes any new messages to this connection, and javascript adds them to the interface so they appear simultaneously, almost as soon as the server receives them?
I know there are some polling options that require you to install some apache modules etc, but I'm pretty bad of a sysadmin, therefore I'd prefer if there was a very easy to install solution on a shared hosting account, or a php/mysql only solution.
Chat with PHP/AJAX/JSON
I used this book/tutorial to write my chat application:
AJAX and PHP: Building Responsive Web Applications: Chapter 5: AJAX chat and JSON.
It shows how to write a complete chat script from scratch.
Comet based chat
You can also use Comet with PHP.
From: zeitoun:
Comet enables web servers to send data to the client without having any need for the client to request it. Therefor, this technique will produce more responsive applications than classic AJAX. In classic AJAX applications, web browser (client) cannot be notified in real time that the server data model has changed. The user must create a request (for example by clicking on a link) or a periodic AJAX request must happen in order to get new data fro the server.
I'll show you two ways to implement Comet with PHP. For example:
based on hidden <iframe> using server timestamp
based on a classic AJAX non-returning request
The first shows the server date in real time on the clients, the displays a mini-chat.
Method 1: iframe + server timestamp
You need:
a backend PHP script to handle the persistent http request backend.php
a frondend HTML script load Javascript code index.html
the prototype JS library, but you can also use jQuery
The backend script (backend.php) will do an infinite loop and will return the server time as long as the client is connected.
<?php
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Sun, 5 Mar 2012 05:00:00 GMT");
flush();
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Comet php backend</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<script type="text/javascript">
// KHTML browser don't share javascripts between iframes
var is_khtml = navigator.appName.match("Konqueror") || navigator.appVersion.match("KHTML");
if (is_khtml)
{
var prototypejs = document.createElement('script');
prototypejs.setAttribute('type','text/javascript');
prototypejs.setAttribute('src','prototype.js');
var head = document.getElementsByTagName('head');
head[0].appendChild(prototypejs);
}
// load the comet object
var comet = window.parent.comet;
</script>
<?php
while(1) {
echo '<script type="text/javascript">';
echo 'comet.printServerTime('.time().');';
echo '</script>';
flush(); // used to send the echoed data to the client
sleep(1); // a little break to unload the server CPU
}
?>
</body>
</html>
The frontend script (index.html) creates a "comet" javascript object that will connect the backend script to the time container tag.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Comet demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="prototype.js"></script>
</head>
<body>
<div id="content">The server time will be shown here</div>
<script type="text/javascript">
var comet = {
connection : false,
iframediv : false,
initialize: function() {
if (navigator.appVersion.indexOf("MSIE") != -1) {
// For IE browsers
comet.connection = new ActiveXObject("htmlfile");
comet.connection.open();
comet.connection.write("<html>");
comet.connection.write("<script>document.domain = '"+document.domain+"'");
comet.connection.write("</html>");
comet.connection.close();
comet.iframediv = comet.connection.createElement("div");
comet.connection.appendChild(comet.iframediv);
comet.connection.parentWindow.comet = comet;
comet.iframediv.innerHTML = "<iframe id='comet_iframe' src='./backend.php'></iframe>";
} else if (navigator.appVersion.indexOf("KHTML") != -1) {
// for KHTML browsers
comet.connection = document.createElement('iframe');
comet.connection.setAttribute('id', 'comet_iframe');
comet.connection.setAttribute('src', './backend.php');
with (comet.connection.style) {
position = "absolute";
left = top = "-100px";
height = width = "1px";
visibility = "hidden";
}
document.body.appendChild(comet.connection);
} else {
// For other browser (Firefox...)
comet.connection = document.createElement('iframe');
comet.connection.setAttribute('id', 'comet_iframe');
with (comet.connection.style) {
left = top = "-100px";
height = width = "1px";
visibility = "hidden";
display = 'none';
}
comet.iframediv = document.createElement('iframe');
comet.iframediv.setAttribute('src', './backend.php');
comet.connection.appendChild(comet.iframediv);
document.body.appendChild(comet.connection);
}
},
// this function will be called from backend.php
printServerTime: function (time) {
$('content').innerHTML = time;
},
onUnload: function() {
if (comet.connection) {
comet.connection = false; // release the iframe to prevent problems with IE when reloading the page
}
}
}
Event.observe(window, "load", comet.initialize);
Event.observe(window, "unload", comet.onUnload);
</script>
</body>
</html>
Method 2: AJAX non-returning request
You need the same as in method 1 + a file for dataexchange (data.txt)
Now, backend.php will do 2 things:
Write into "data.txt" when new messages are sent
Do an infinite loop as long as "data.txt" file is unchanged
<?php
$filename = dirname(__FILE__).'/data.txt';
// store new message in the file
$msg = isset($_GET['msg']) ? $_GET['msg'] : '';
if ($msg != '')
{
file_put_contents($filename,$msg);
die();
}
// infinite loop until the data file is not modified
$lastmodif = isset($_GET['timestamp']) ? $_GET['timestamp'] : 0;
$currentmodif = filemtime($filename);
while ($currentmodif <= $lastmodif) // check if the data file has been modified
{
usleep(10000); // sleep 10ms to unload the CPU
clearstatcache();
$currentmodif = filemtime($filename);
}
// return a json array
$response = array();
$response['msg'] = file_get_contents($filename);
$response['timestamp'] = $currentmodif;
echo json_encode($response);
flush();
?>
The frontend script (index.html) creates the <div id="content"></div> tags hat will contains the chat messages comming from "data.txt" file, and finally it create a "comet" javascript object that will call the backend script in order to watch for new chat messages.
The comet object will send AJAX requests each time a new message has been received and each time a new message is posted. The persistent connection is only used to watch for new messages. A timestamp url parameter is used to identify the last requested message, so that the server will return only when the "data.txt" timestamp is newer that the client timestamp.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Comet demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="prototype.js"></script>
</head>
<body>
<div id="content">
</div>
<p>
<form action="" method="get" onsubmit="comet.doRequest($('word').value);$('word').value='';return false;">
<input type="text" name="word" id="word" value="" />
<input type="submit" name="submit" value="Send" />
</form>
</p>
<script type="text/javascript">
var Comet = Class.create();
Comet.prototype = {
timestamp: 0,
url: './backend.php',
noerror: true,
initialize: function() { },
connect: function()
{
this.ajax = new Ajax.Request(this.url, {
method: 'get',
parameters: { 'timestamp' : this.timestamp },
onSuccess: function(transport) {
// handle the server response
var response = transport.responseText.evalJSON();
this.comet.timestamp = response['timestamp'];
this.comet.handleResponse(response);
this.comet.noerror = true;
},
onComplete: function(transport) {
// send a new ajax request when this request is finished
if (!this.comet.noerror)
// if a connection problem occurs, try to reconnect each 5 seconds
setTimeout(function(){ comet.connect() }, 5000);
else
this.comet.connect();
this.comet.noerror = false;
}
});
this.ajax.comet = this;
},
disconnect: function()
{
},
handleResponse: function(response)
{
$('content').innerHTML += '<div>' + response['msg'] + '</div>';
},
doRequest: function(request)
{
new Ajax.Request(this.url, {
method: 'get',
parameters: { 'msg' : request
});
}
}
var comet = new Comet();
comet.connect();
</script>
</body>
</html>
Alternatively
You can also have a look at other chat applications to see how they did it:
http://hot-things.net/?q=blite - BlaB! Lite is an AJAX based and best viewed with any browser chat system that supports MySQL, SQLite & PostgreSQL databases.
Gmail/Facebook Style jQuery Chat - This jQuery chat module enables you to seamlessly integrate Gmail/Facebook style chat into your existing website.
Writing a JavaScript/PHP Chat Server - A tutorial
CometChat - CometChat runs on standard shared servers. Only PHP + mySQL required.
Polling is not a good idea. You need a solution that use long polling or web sockets.
http://hookbox.org is probably the best tool you can use.
It is a box that lives between the server and the browsers and manages abstractions called channels (think about an IRC channel). It is open source on github: https://github.com/hookbox/hookbox The box is written in Python but it can easily be used with a server written in any language. It also come with a Javascript library that is built on jsio (uses websockets, long-polling, or whatever is the best technology available on the browser) that guarantee that it uses the best technology available in the browsers.In a demo I saw a realtime chat implemented with few line of code.
Hookbox’s purpose is to ease the development of real-time web applications, with an emphasis on tight integration with existing web technology. Put simply, Hookbox is a web-enabled message queue. Browers may directly connect to Hookbox, subscribe to named channels, and publish and receive messages on those channels in real-time. An external application (typically the web application itself) may also publish messages to channels by means of the Hookbox REST interface. All authentication and authorization is performed by an external web application via designated “webhook” callbacks.
Any time a user connects or operates on a channel, ( subscribe, publish, unsubscribe) Hookbox makes an http request to the web application for authorization for the action. Once subscribed to a channel, the user’s browser will receive real-time events that originate either in another browser via the javascript api, or from the web application via the REST api.
They key insight is that all application development with hookbox Happens either in javascript, or in the native language of the web application itself (e.g. PHP.)
You need a server that can run Python BUT you do NOT have to know Python.
If instead you want to use just websockets and PHP this is good starting point: http://blancer.com/tutorials/69066/start-using-html5-websockets-today/
Have you looked at PHPDaemon, which is written with active usage of libevent and pnctl? It has lots of features and even simple chat demo application. Even it has some production implementations.
this could be a good starting point
http://css-tricks.com/jquery-php-chat/
I suggest to implement it with HTML5 WebSockets, with long polling or comet as a fallback for older browsers. WebSockets open a persistent connection to the browser.
There is an open source php implementation of a websocket server.
I suggest you to try Socket.IO together with NodeJS. Socket.IO gives you a nice and very easy client API, works on most modern browsers and uses appropriate transport where possible (Websocket, long polling, etc). NodeJS is a server-side daemon, which holds HTTP connections. Official site of the Socket.IO contains information on how to use them together. Hope it will help you.
I believe the problem you are looking at requires the use of comet web programming. You can find more details on wikipedia, by searching for Comet programming, and on Ajaxian (I'm still new to this site and I can't post more than 1 link in the response).
The problem is that this can't be easily achieved with php on the server side. More details:
using comet with php
Also, if you search on google for 'php comet' you'll find a tutorial to achieve the desired effect.
LATER EDIT
Ape project
Implemented a project using this engine. Is great.
Comet with php
Hope this helps,
Gabriel
This looks promising! Might even be super easy to restyle :)
http://www.php-development.ru/javascripts/ajax-chat.php
Ajax Chat script in Javascript/PHP
Description
Ajax Chat is a light-weight customizable web chat software implemented in JavaScript and PHP. The script does not require Java, Flash, or any other plugins.
Features
Public and private chat.
Login as a registered user or as a guest.
Away status, custom colors, smileys, user gender/status icons.
Ajax Chat can be integrated with a third-party membership system by implementing user authentication routine. Advanced integration options: if user is logged in to the website, he can be logged in to the chat automatically.
*Please note that this is a copy/paste from the original site.
I haven't done it with PHP before but you're best bet would probably be some kind of socket connection. Here's the PHP manual for sockets.
I don't remember who's tutorial it was but I made a chat room like what you want using Flash for the client and Java for the server. I think this link might be where the tutorial was and it may help you out.
I've got a web page that allows to start a certain process and then redirects to another page that displays log file of that process. Since execution takes up to 10 minutes, I want log page to autoupdate itself or load data from the file periodically.
Right now I added
<meta http-equiv="refresh" content="5;url=log.php#bottom" />
to html/head but wondering if there may be a better solution. Can someone give any advice on aproaching this problem?
I do it this way:
var current_length = 0;
function update() {
setTimeout(update, 3000);
$.post("/update_url", { 'current_length': current_length }, function(data) {
if (data.current_length != current_length) return; //it's too old answer
$("#log").html($("#log").html() + data.text);
current_length += data.text.length;
}, "json");
}
update();
The server must skip several bytes at beginning and send json with current_length and the rest of file.
I prefer using memcached to store process output.
You could:
Periodically poll the server to see if there are more messages, basically you would call a PHP script with javascript and would pass the length of the log file in the last poll and then insert into the document the new data. The server would return all the data after that offset and also the new length.
(simpler) Make a long lived PHP script that keeps reading the file and echo and flush it as soon as there's new data. See PHP: How to read a file live that is constantly being written to.
Use AJAX to do this. Easy in jQuery:
<script type="text/javascript">
$(function(){
window.setInterval('updateLog()', 5000);
});
function updateLog() {
$.get('log.php');
}
</script>
Why not use javascript?
Use setInterval and run an AJAX call to log.php periodically.
You could also use an iframe, but the AJAX perdiodical call is a better way of doing it in my opinion.
I can find lots of information on how Long Polling works (For example, this, and this), but no simple examples of how to implement this in code.
All I can find is cometd, which relies on the Dojo JS framework, and a fairly complex server system..
Basically, how would I use Apache to serve the requests, and how would I write a simple script (say, in PHP) which would "long-poll" the server for new messages?
The example doesn't have to be scaleable, secure or complete, it just needs to work!
It's simpler than I initially thought.. Basically you have a page that does nothing, until the data you want to send is available (say, a new message arrives).
Here is a really basic example, which sends a simple string after 2-10 seconds. 1 in 3 chance of returning an error 404 (to show error handling in the coming Javascript example)
msgsrv.php
<?php
if(rand(1,3) == 1){
/* Fake an error */
header("HTTP/1.0 404 Not Found");
die();
}
/* Send a string after a random number of seconds (2-10) */
sleep(rand(2,10));
echo("Hi! Have a random number: " . rand(1,10));
?>
Note: With a real site, running this on a regular web-server like Apache will quickly tie up all the "worker threads" and leave it unable to respond to other requests.. There are ways around this, but it is recommended to write a "long-poll server" in something like Python's twisted, which does not rely on one thread per request. cometD is an popular one (which is available in several languages), and Tornado is a new framework made specifically for such tasks (it was built for FriendFeed's long-polling code)... but as a simple example, Apache is more than adequate! This script could easily be written in any language (I chose Apache/PHP as they are very common, and I happened to be running them locally)
Then, in Javascript, you request the above file (msg_srv.php), and wait for a response. When you get one, you act upon the data. Then you request the file and wait again, act upon the data (and repeat)
What follows is an example of such a page.. When the page is loaded, it sends the initial request for the msgsrv.php file.. If it succeeds, we append the message to the #messages div, then after 1 second we call the waitForMsg function again, which triggers the wait.
The 1 second setTimeout() is a really basic rate-limiter, it works fine without this, but if msgsrv.php always returns instantly (with a syntax error, for example) - you flood the browser and it can quickly freeze up. This would better be done checking if the file contains a valid JSON response, and/or keeping a running total of requests-per-minute/second, and pausing appropriately.
If the page errors, it appends the error to the #messages div, waits 15 seconds and then tries again (identical to how we wait 1 second after each message)
The nice thing about this approach is it is very resilient. If the clients internet connection dies, it will timeout, then try and reconnect - this is inherent in how long polling works, no complicated error-handling is required
Anyway, the long_poller.htm code, using the jQuery framework:
<html>
<head>
<title>BargePoller</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript" charset="utf-8"></script>
<style type="text/css" media="screen">
body{ background:#000;color:#fff;font-size:.9em; }
.msg{ background:#aaa;padding:.2em; border-bottom:1px #000 solid}
.old{ background-color:#246499;}
.new{ background-color:#3B9957;}
.error{ background-color:#992E36;}
</style>
<script type="text/javascript" charset="utf-8">
function addmsg(type, msg){
/* Simple helper to add a div.
type is the name of a CSS class (old/new/error).
msg is the contents of the div */
$("#messages").append(
"<div class='msg "+ type +"'>"+ msg +"</div>"
);
}
function waitForMsg(){
/* This requests the url "msgsrv.php"
When it complete (or errors)*/
$.ajax({
type: "GET",
url: "msgsrv.php",
async: true, /* If set to non-async, browser shows page as "Loading.."*/
cache: false,
timeout:50000, /* Timeout in ms */
success: function(data){ /* called when request to barge.php completes */
addmsg("new", data); /* Add response to a .msg div (with the "new" class)*/
setTimeout(
waitForMsg, /* Request next message */
1000 /* ..after 1 seconds */
);
},
error: function(XMLHttpRequest, textStatus, errorThrown){
addmsg("error", textStatus + " (" + errorThrown + ")");
setTimeout(
waitForMsg, /* Try again after.. */
15000); /* milliseconds (15seconds) */
}
});
};
$(document).ready(function(){
waitForMsg(); /* Start the inital request */
});
</script>
</head>
<body>
<div id="messages">
<div class="msg old">
BargePoll message requester!
</div>
</div>
</body>
</html>
I've got a really simple chat example as part of slosh.
Edit: (since everyone's pasting their code in here)
This is the complete JSON-based multi-user chat using long-polling and slosh. This is a demo of how to do the calls, so please ignore the XSS problems. Nobody should deploy this without sanitizing it first.
Notice that the client always has a connection to the server, and as soon as anyone sends a message, everyone should see it roughly instantly.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Copyright (c) 2008 Dustin Sallings <dustin+html#spy.net> -->
<html lang="en">
<head>
<title>slosh chat</title>
<script type="text/javascript"
src="http://code.jquery.com/jquery-latest.js"></script>
<link title="Default" rel="stylesheet" media="screen" href="style.css" />
</head>
<body>
<h1>Welcome to Slosh Chat</h1>
<div id="messages">
<div>
<span class="from">First!:</span>
<span class="msg">Welcome to chat. Please don't hurt each other.</span>
</div>
</div>
<form method="post" action="#">
<div>Nick: <input id='from' type="text" name="from"/></div>
<div>Message:</div>
<div><textarea id='msg' name="msg"></textarea></div>
<div><input type="submit" value="Say it" id="submit"/></div>
</form>
<script type="text/javascript">
function gotData(json, st) {
var msgs=$('#messages');
$.each(json.res, function(idx, p) {
var from = p.from[0]
var msg = p.msg[0]
msgs.append("<div><span class='from'>" + from + ":</span>" +
" <span class='msg'>" + msg + "</span></div>");
});
// The jQuery wrapped msgs above does not work here.
var msgs=document.getElementById("messages");
msgs.scrollTop = msgs.scrollHeight;
}
function getNewComments() {
$.getJSON('/topics/chat.json', gotData);
}
$(document).ready(function() {
$(document).ajaxStop(getNewComments);
$("form").submit(function() {
$.post('/topics/chat', $('form').serialize());
return false;
});
getNewComments();
});
</script>
</body>
</html>
Tornado is designed for long-polling, and includes a very minimal (few hundred lines of Python) chat app in /examples/chatdemo , including server code and JS client code. It works like this:
Clients use JS to ask for an updates since (number of last message), server URLHandler receives these and adds a callback to respond to the client to a queue.
When the server gets a new message, the onmessage event fires, loops through the callbacks, and sends the messages.
The client-side JS receives the message, adds it to the page, then asks for updates since this new message ID.
I think the client looks like a normal asynchronous AJAX request, but you expect it to take a "long time" to come back.
The server then looks like this.
while (!hasNewData())
usleep(50);
outputNewData();
So, the AJAX request goes to the server, probably including a timestamp of when it was last update so that your hasNewData() knows what data you have already got.
The server then sits in a loop sleeping until new data is available. All the while, your AJAX request is still connected, just hanging there waiting for data.
Finally, when new data is available, the server gives it to your AJAX request and closes the connection.
Here are some classes I use for long-polling in C#. There are basically 6 classes (see below).
Controller: Processes actions required to create a valid response (db operations etc.)
Processor: Manages asynch communication with the web page (itself)
IAsynchProcessor: The service processes instances that implement this interface
Sevice: Processes request objects that implement IAsynchProcessor
Request: The IAsynchProcessor wrapper containing your response (object)
Response: Contains custom objects or fields
This is a nice 5-minute screencast on how to do long polling using PHP & jQuery:
http://screenr.com/SNH
Code is quite similar to dbr's example above.
Here is a simple long-polling example in PHP by Erik Dubbelboer using the Content-type: multipart/x-mixed-replace header:
<?
header('Content-type: multipart/x-mixed-replace; boundary=endofsection');
// Keep in mind that the empty line is important to separate the headers
// from the content.
echo 'Content-type: text/plain
After 5 seconds this will go away and a cat will appear...
--endofsection
';
flush(); // Don't forget to flush the content to the browser.
sleep(5);
echo 'Content-type: image/jpg
';
$stream = fopen('cat.jpg', 'rb');
fpassthru($stream);
fclose($stream);
echo '
--endofsection
';
And here is a demo:
http://dubbelboer.com/multipart.php
I used this to get to grips with Comet, I have also set up Comet using the Java Glassfish server and found lots of other examples by subscribing to cometdaily.com
Take a look at this blog post which has code for a simple chat app in Python/Django/gevent.
Below is a long polling solution I have developed for Inform8 Web. Basically you override the class and implement the loadData method. When the loadData returns a value or the operation times out it will print the result and return.
If the processing of your script may take longer than 30 seconds you may need to alter the set_time_limit() call to something longer.
Apache 2.0 license. Latest version on github
https://github.com/ryanhend/Inform8/blob/master/Inform8-web/src/config/lib/Inform8/longpoll/LongPoller.php
Ryan
abstract class LongPoller {
protected $sleepTime = 5;
protected $timeoutTime = 30;
function __construct() {
}
function setTimeout($timeout) {
$this->timeoutTime = $timeout;
}
function setSleep($sleep) {
$this->sleepTime = $sleepTime;
}
public function run() {
$data = NULL;
$timeout = 0;
set_time_limit($this->timeoutTime + $this->sleepTime + 15);
//Query database for data
while($data == NULL && $timeout < $this->timeoutTime) {
$data = $this->loadData();
if($data == NULL){
//No new orders, flush to notify php still alive
flush();
//Wait for new Messages
sleep($this->sleepTime);
$timeout += $this->sleepTime;
}else{
echo $data;
flush();
}
}
}
protected abstract function loadData();
}
This is one of the scenarios that PHP is a very bad choice for. As previously mentioned, you can tie up all of your Apache workers very quickly doing something like this. PHP is built for start, execute, stop. It's not built for start, wait...execute, stop. You'll bog down your server very quickly and find that you have incredible scaling problems.
That said, you can still do this with PHP and have it not kill your server using the nginx HttpPushStreamModule: http://wiki.nginx.org/HttpPushStreamModule
You setup nginx in front of Apache (or whatever else) and it will take care of holding open the concurrent connections. You just respond with payload by sending data to an internal address which you could do with a background job or just have the messages fired off to people that were waiting whenever the new requests come in. This keeps PHP processes from sitting open during long polling.
This is not exclusive to PHP and can be done using nginx with any backend language. The concurrent open connections load is equal to Node.js so the biggest perk is that it gets you out of NEEDING Node for something like this.
You see a lot of other people mentioning other language libraries for accomplishing long polling and that's with good reason. PHP is just not well built for this type of behavior naturally.
Thanks for the code, dbr. Just a small typo in long_poller.htm around the line
1000 /* ..after 1 seconds */
I think it should be
"1000"); /* ..after 1 seconds */
for it to work.
For those interested, I tried a Django equivalent. Start a new Django project, say lp for long polling:
django-admin.py startproject lp
Call the app msgsrv for message server:
python manage.py startapp msgsrv
Add the following lines to settings.py to have a templates directory:
import os.path
PROJECT_DIR = os.path.dirname(__file__)
TEMPLATE_DIRS = (
os.path.join(PROJECT_DIR, 'templates'),
)
Define your URL patterns in urls.py as such:
from django.views.generic.simple import direct_to_template
from lp.msgsrv.views import retmsg
urlpatterns = patterns('',
(r'^msgsrv\.php$', retmsg),
(r'^long_poller\.htm$', direct_to_template, {'template': 'long_poller.htm'}),
)
And msgsrv/views.py should look like:
from random import randint
from time import sleep
from django.http import HttpResponse, HttpResponseNotFound
def retmsg(request):
if randint(1,3) == 1:
return HttpResponseNotFound('<h1>Page not found</h1>')
else:
sleep(randint(2,10))
return HttpResponse('Hi! Have a random number: %s' % str(randint(1,10)))
Lastly, templates/long_poller.htm should be the same as above with typo corrected. Hope this helps.
Why not consider the web sockets instead of long polling? They are much efficient and easy to setup. However they are supported only in modern browsers. Here is a quick reference.
The WS-I group published something called "Reliable Secure Profile" that has a Glass Fish and .NET implementation that apparently inter-operate well.
With any luck there is a Javascript implementation out there as well.
There is also a Silverlight implementation that uses HTTP Duplex. You can connect javascript to the Silverlight object to get callbacks when a push occurs.
There are also commercial paid versions as well.
For a ASP.NET MVC implementation, look at SignalR which is available on NuGet.. note that the NuGet is often out of date from the Git source which gets very frequent commits.
Read more about SignalR on a blog on by Scott Hanselman
You can try icomet(https://github.com/ideawu/icomet), a C1000K C++ comet server built with libevent. icomet also provides a JavaScript library, it is easy to use as simple as
var comet = new iComet({
sign_url: 'http://' + app_host + '/sign?obj=' + obj,
sub_url: 'http://' + icomet_host + '/sub',
callback: function(msg){
// on server push
alert(msg.content);
}
});
icomet supports a wide range of Browsers and OSes, including Safari(iOS, Mac), IEs(Windows), Firefox, Chrome, etc.
Simplest NodeJS
const http = require('http');
const server = http.createServer((req, res) => {
SomeVeryLongAction(res);
});
server.on('clientError', (err, socket) => {
socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
});
server.listen(8000);
// the long running task - simplified to setTimeout here
// but can be async, wait from websocket service - whatever really
function SomeVeryLongAction(response) {
setTimeout(response.end, 10000);
}
Production wise scenario in Express for exmaple you would get response in the middleware. Do you what you need to do, can scope out all of the long polled methods to Map or something (that is visible to other flows), and invoke <Response> response.end() whenever you are ready. There is nothing special about long polled connections. Rest is just how you normally structure your application.
If you dont know what i mean by scoping out, this should give you idea
const http = require('http');
var responsesArray = [];
const server = http.createServer((req, res) => {
// not dealing with connection
// put it on stack (array in this case)
responsesArray.push(res);
// end this is where normal api flow ends
});
server.on('clientError', (err, socket) => {
socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
});
// and eventually when we are ready to resolve
// that if is there just to ensure you actually
// called endpoint before the timeout kicks in
function SomeVeryLongAction() {
if ( responsesArray.length ) {
let localResponse = responsesArray.shift();
localResponse.end();
}
}
// simulate some action out of endpoint flow
setTimeout(SomeVeryLongAction, 10000);
server.listen(8000);
As you see, you could really respond to all connections, one, do whatever you want. There is id for every request so you should be able to use map and access specific out of api call.