hello, world websocket in quercus/php

A "hello, world" WebSocket servlet using the Quercus PHP implementation

Demo

WebSocket is a new browser capability being developed for HTML 5 browsers, enabling fully interactive applications. With WebSockets, both the browser and the server can send asynchronous messages over a single TCP socket, without resorting to long polling or comet.

Essentially, a WebSocket is a standard bidirectional TCP socket between the client and the server. The socket starts out as a HTTP connection and then "Upgrades" to a TCP socket after a HTTP handshake. After the handshake, either side can send data.

GET /test HTTP/1.1
Upgrade: WebSocket
Connection: Upgrade
Origin: http://localhost/test
Host: localhost
Content-Length: 0

...

HTTP/1.1 101 Web Socket Protocol Handshake
Upgrade: WebSocket
Connection: Upgrade
Server: Resin/4.0.2
WebSocket-Location: ws://localhost/websocket
WebSocket-Origin: http://localhost/test
Content-Length: 0
Date: Fri, 08 May 2009 09:51:31 GMT

...

x00 utf-8-data xff

\x00hello, world\xff

Since the tutorial is a hello, world, the JavaScript just does the following:

1. Connects to the Resin WebSocket servlet
2. Sends a "hello" query to the servlet
3. Sends a "server" query to the servlet
4. Displays any received messages from the servlet

The JavaScript for this example has been tested with the nightly build of Chromium.

<?php
  $url = "ws://localhost:8080/example/websocket";
?>

<script language='javascript'>

function onopen(event) { ... }
function onmessage(event) { ... }
function onclose(event) { ... }

ws = new WebSocket("<?= $url ?>");
wsopen.ws = ws;
ws.onopen = wsopen;
ws.onmessage = wsmessage;
ws.onclose = wsclose;

</script>

<script language='javascript'>

function wsmessage(event)
{
  data = event.data;

  alert("Received: [" + data + "]");
}

</script>

<script language='javascript'>

function wsopen(event)
{
  ws = this.ws;

  ws.send("my-message");
}

ws = new WebSocket(...);
wsopen.ws = ws;
ws.onopen = wsopen;

</script>

Resin's WebSocket PHP support requires two PHP files. The first accepts the WebSocket request and Upgrades the HTTP request. The second handles WebSocket messages.

To upgrade a HTTP socket to WebSocket, use websocket_start(path). The path is a PHP include path to handle the request.

<?php

$ws = websocket_start("websocket-handler.php");

The WebSocket handler is the heart of the server-side implementation of websockets. It is a single-threaded listener for client events.

When a new packet is available, Resin will call the script, expecting it to read data from the client. While the handler is processing, Resin will not call it again until the first one has completed processing.

In this example, the handler reads a WebSocket text packet and sends a response.

<?php

// read the next packet from the client 
$value = websocket_read();

if ($value == "hello") {
 websocket_write("world");
} 
else if ($value == "server") {
 websocket_write("Resin PHP");
}

Demo