Lynne Lynne - 1 month ago 11
PHP Question

I am trying to implement a pulse into a PHP Ratchet Websocket Application

Hello Stack Overflow,

I am building a browser-based text only multi-player RPG written in PHP with Ratchet as the backbone.

What I have so far: It works very well. I have implemented a simple and effective command interpretor that does a good job of transferring data between the client and server. I'm able to easily perform database operations and instantiate outside classes inside my Server class to use to pass information back to the client.

Where I've gotten stuck: For some reason, my brain broke trying to implement ticks, which in the context of my game, is a set of events that happens every 45 seconds. It's basically the heartbeat of the game, and I can't move forward without having a reliable and graceful implementation of it. The tick needs to do a multitude of things, including (but not limited to): sending messages to players, updating player regen, memory handling, and so on. Generally, all these actions can be coded and placed in an Update class.

But I can't figure out how to get the tick to actually happen. The tick itself, just a function that occurs every 45 seconds inside my react loop, it should start when the server starts. It absolutely needs to be server-side. I could technically implement it client-side and sync with values in a database but I do NOT want to go down that road.

I feel like this should be easier than my brain is making it.

What I've tried:
I've tried running a simple recursive function that constructs my update class on a timer using sleep(45), but again, this needs to start when the server starts, and if I toss an infinite looping function in the construct of my server class, the startup script never gets passed that and the game never starts.

I've tried using the onPeriodicTimer function that comes with react, but I can't figure out how to implement it..

I've tried something crazy like using node js to send a message to my server every 45 seconds and my interpreter catches that particular message and starts the tick process. This is the closest I've gotten to a successful implementation but I'm really hoping to be able to do it without a client having to connect and talk to the server, it seems hackey.

I've tried ZeroMQ to achieve the same goal as above (a client that sends a message to my server that triggers the update) but again, I don't want to have to have a client listener constantly connected for the game to run, and also, zeroMQ is a lot to deal with for something so small.. I had no luck with it.

There has to be a better way to achieve this. Any help would be appreciated.

For reference, here is a basic outline of out my socket application is working. To start, I used the "Hello World" tutorial on the Ratchet website.

So I have a startup.php script that I run to initialize the Server class, which accepts messages from connected clients. onMessage, an interpretor class is instantiated which parses the message out and looks for the command the client passed in a database table which loads the corresponding Class and Method for that command, that data is based back to the onMessage function, the class and method for the command is called, and the result is passed back to the client.

TLDR: How do I add a repeating function to a Ratchet websocket server that can send messages to connected clients every 45 seconds?

Here's the Server class:

class Server implements MessageComponentInterface

{
public $clients;

public function __construct()
{
$this->clients = new \SplObjectStorage;
//exec("nodejs ../bin/java.js", $output);
}

public function onOpen(ConnectionInterface $conn)
{
$conn->connected_state = 0;
$this->clients->attach($conn);

// Initiate login
$login = new Login('CONN_GETNAME');

if($login->success)
{
$conn->send($login->output);
$conn->connected_state = $login->new_state;
$conn->chData = new Character();
}

echo "New connection! ({$conn->resourceId})\n";
}

public function onMessage(ConnectionInterface $from, $msg)
{
if($msg == 'do_tick')
{
echo "a tick happened <br>";

}
else
{
if($from->connected_state == 'CONN_CONNECTED' || $msg == 'chardump')
{
$interpretor = new Interpret($msg);

if($interpretor->success)
{
$action_class_var = $interpretor->class;
$action_method_var = $interpretor->function;

$action_class = new $action_class_var($this->clients, $from, $interpretor->msg);
$action = $action_class->{$action_method_var}();

foreach($this->clients as $client)
{
if($action->to_room)
{
if($from != $client)
{
$client->send($action->to_room);
}
}

if($action->to_global)
{
if($from != $client)
{
$client->send($action->to_global);
}
}

if($action->to_char)
{

$client->send($action->to_char);
}
}
}
else
{
$from->send('Huh?');
}
}
else
{
$login = new Login($from->connected_state, $msg, $from);

$from->connected_state = $login->new_state;

if($login->char_data && count($login->char_data)>0)
{
foreach($login->char_data as $key=>$val)
{
$from->chData->{$key} = $val;
}
}

$from->send($login->output);
}
}
}

public function onClose(ConnectionInterface $conn) {
$this->clients->detach($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();
}


Perhaps an onTick function added to this class that gets called every X seconds? Is that possible?

Answer

To broadcast the message to everyone in intervals of 45 seconds (or any other number), you must control the event loop which Ratchet uses.

You need to add a timed event, various vendors call this timed event, timer event, repeatable event, but it always behaves the same - a function fires after X amount of time.

Class that you are after is documented at this link

Alternatively, you can use icicle instead of Ratchet. I personally prefer it, I don't have any particular reason for the preference - both libraries are excellent in my opinion, and it's always nice to have an alternative.

Interestingly enough, you tried to use ZeroMQ - it's a transport layer and it's definitely one of the best libraries / projects I've ever used. It plays nicely with event loops, it's definitely interesting for developing distributed systems, job queues and similar.

Good luck with your game! If you'll have any other questions regarding WS, scaling to multiple machines or similar - feel free to ping me in the comments below this answer.