What are WebSockets?

Like TCP but designed to compliment HTTP

Standardizes the hacks that have been layered on HTTP (like Comet)

Created for low-latency communication

Full Duplex

Message-based

Extensible

Use Cases

• Multiplayer Games
• Coordinated Interactive experiments
• Chat / Presence
• Realtime Data Tickers and Charts
• Data interactions, such as distributed resource locking
• Nearly anything that would normally be done over TCP (besides streams)

Browser Support

What does it look like?

But you don't need to know that to use it

Enter Ratchet and Javascript

What is Ratchet?

Ratchet is a WebSocket server built on ReactPHP

But wait!

Node.js and friends are daemons.

PHP doesn't do that!

ReactPHP and Ratchet makes it happen.

<?php 
use Ratchet\MessageComponentInterface; 
use Ratchet\ConnectionInterface; 

class Chat implements MessageComponentInterface { 
    public function onOpen(ConnectionInterface $conn) { 
    } 

    public function onMessage(ConnectionInterface $from, $msg) { 
    } 

    public function onClose(ConnectionInterface $conn) { 
    } 

    public function onError(ConnectionInterface $conn, \Exception $e) { 
    } 
}

Best Practices

PHP Environment: libevent, ulimit, no xdebug

Use port 80, 443 for best compatibility

Run on subdomain: ws.example.com

Okay, so show me how to do something.

Problems

Workflow

Red, Restart, Refactor

Deployment

Long running; not stateless like traditional php

When code changes server needs be restarted

We are not sysadmins

Use a daemon manager and automate restarting

Rocketeer or Capistrano will be your friend

Advanced Topics

WAMP

Ratchet Component

public function onCall(ConnectionInterface $conn, string $id, Topic $topic, array $params)
public function onSubscribe(ConnectionInterface $conn, Topic $topic)
public function onUnsubscribe(ConnectionInterface $conn, Topic $topic)
public function onPublish(ConnectionInterface $conn, Topic $topic, string $event)

Ratchet Connection

public function event (string $topic, string $msg) - Publish/Send data to a client that has subscribed to a topic
public function callResult (string $id, array $data) - A response to a client Call. Make sure to pass the corresponding $id from the onCall event
public function callError (string $id, string $topic, string $desc = '', string $details = null)

Client: Autobahnjs

Servers and Load Balancing

Reverse proxy (HAProxy or Varnish)

nginx > 1.3.13: http://nginx.org/en/docs/http/websocket.html

Apache 2.4 mod_proxy_wstunnel: http://httpd.apache.org/docs/2.4/mod/mod_proxy_wstunnel.html