How to build a Web Socket Connection? - php

Question

In my Android project I want to implement Web Sockets. So first I tried to integrate the server-side Websockets and tried to test it in the command line. The following link shows how I tried to open the Web Socket Connection. I tried to reach the Port which is created in the Web socket connection and it worked! But when I attached a message I never receive it. Maybe that’s because the onMessage function is not triggered?
https://i.stack.imgur.com/N8tsf.jpg
Additionally I used following code to open the Websocket connection and send a message.
?php
ini_set('display_errors',1);
use Ratchet\MessageComponentInterface;
use Ratchet\ConnectionInterface;
use Ratchet\Server\IoServer;
use Ratchet\Http\HttpServer;
use Ratchet\WebSocket\WsServer;
require_once '/var/www/vendor/autoload.php';
class Chat implements MessageComponentInterface {
protected $clients;
public function __construct() {
$this->clients = new \SplObjectStorage;
}
public function onOpen(ConnectionInterface $conn) {
// Store the new connection to send messages to later
$this->clients->attach($conn);
echo "New connection! ({$conn->resourceId})\n";
}
public function onMessage(ConnectionInterface $from, $msg) {
$numRecv = count($this->clients) - 1;
echo sprintf('Connection %d sending message "%s" to %d other connection%s' . "\n"
, $from->resourceId, $msg, $numRecv, $numRecv == 1 ? '' : 's');
foreach ($this->clients as $client) {
if ($from !== $client) {
// The sender is not the receiver, send to each client connected
$client->send($msg);
}
}
}
public function onClose(ConnectionInterface $conn) {
// The connection is closed, remove it, as we can no longer send it messages
$this->clients->detach($conn);
echo "Connection {$conn->resourceId} has disconnected\n";
}
public function onError(ConnectionInterface $conn, \Exception $e) {
echo "An error has occurred: {$e->getMessage()}\n";
$conn->close();
}
}
$server = IoServer::factory(
new HttpServer(
new WsServer(
new Chat()
)
),
8081
);
$server->run();
?>
There aren't any errors if I run php app.php. So actually it should work to send a message and receive it? Furthermore the onMessage function doesn't seem to be triggered. But if I add an echo in the public function __construct() function it is printed, so it might be the only function which is executed.
I hope someone can help me to receive and print messages in this Web Socket Connection.
Thanks for your help!

Answer 1

A websocket is a socket, but a socket is not necessarily a websocket. Telnet doesn't work well with testing websockets, because it connects to the socket, but it doesn't do the handshake.
A websocket is basically a socket that requires an http handshake at the beginning before it can begin sending messages. That's why it looks like the Ratchet program isn't responding. It's waiting for your side of the handshake to be done.
To make it work with your server, you would probably want to get a websocket client on the Android side of things. Or, you could make a server which is just a regular socket server instead of a websocket.
If you get the websocket handshake done correctly, before any message is sent, you should see New connection! in the terminal on the php side, because of what you have in the onOpen function.
If you sent something along the lines of this:
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
Origin: http://example.com
...it might work.
https://en.wikipedia.org/wiki/WebSocket#Protocol_handshake