Problem determining connection was closed

[crimson273]

I'm having problems figuring out the connection was closed. Below is the code example I'm using for testing. It connects to endpoint, sends ping messages to a server every 5 second, and sends pong messages to a server when it gets a ping message from server. It also closes connection on the client side after 30 seconds just for testing purporses. What I am expecting:

• get WebsocketClosedException while attempting to send a ping message after connection was closed
• get EventLoop still working after connection was closed and thus trying to send ping message resulting in WebsocketClosedException
• get onClose callback called when connection is closed (either by client or by server)

What I am getting:

• onClose never gets called, no matter who closed the connection
• no exception at all after the connection is closed - the script just hangs in while loop, EventLoop stops trying to send ping message. This cover both cases of connection being closed on the client and on the server.
• issuing $connection->close() doesn't result on connection actually disappering from the server. The server still 'sees' this connection

In the end I need a reliable way to understand, that the connection was closed. On the server in particular. Any advice is very apriciated.

<?php

require dirname(__DIR__) . '/vendor/autoload.php';

use Revolt\EventLoop;
use function Amp\weakClosure;
use function Amp\Websocket\Client\connect;

$serverUrl = 'ws://dev.sportlevel.com/highway';

$connection = connect($serverUrl);

$connection->onClose(function () {
    echo "connection is closed!" . PHP_EOL;
});

EventLoop::repeat(5, weakClosure(function () use ($connection) {
    $pingMessage = json_encode([
        'msg_type' => 'ping',
        'timestamp' => microtime(true),
    ]);

    echo "sending ping: {$pingMessage}" . PHP_EOL;
    try {
        $connection->sendText($pingMessage);
    } catch (\Exception $e) {
        echo "send ping failed! " . $e->getMessage() . PHP_EOL;
    }

}));

EventLoop::delay(30, function () use ($connection) {
    $connection->close();
});

while (1) {
    if ($message = $connection->receive()) {
        $payload = $message->buffer();

        echo "Received: {$payload}" . PHP_EOL;

        $message = json_decode($payload, true);

        if ($message['msg_type'] == 'ping') {
            $pongMessage = json_encode([
                'msg_type' => 'pong',
                'timestamp' => $message['timestamp'],
            ]);

            echo "send pong: {$pongMessage}" . PHP_EOL;
            try {
                $connection->sendText($pongMessage);
            } catch (\Exception $e) {
                echo "send pong failed! " . $e->getMessage() . PHP_EOL;
            }
        }
    }
}

[crimson273]

ok, I've managed to partially figure this one out.

I've rewritten the code and now I do have everything I needed.

What concerns me is that I don't really understand why the previous example didn't work as I supposed.

Another concern is if the below example is the "right" way of doing things. I can use EventLoop::run() call here while it's description says that I should use Suspension API instead.

I understand that this isn't about websocket client in particular and is really a question of correct usage for Revolt\EventLoop but it is really frustrating that I can't seem to find any verbose description of using it while the official documentation seem lacking.

So, if someone could point me out for any good sources of information about this - I would be very grateful.

Here's an updated code example

<?php

require dirname(__DIR__) . '/vendor/autoload.php';

use Revolt\EventLoop;
use function Amp\weakClosure;
use function Amp\Websocket\Client\connect;

$serverUrl = 'ws://dev.sportlevel.com/highway';

$connection = connect($serverUrl);

$connection->onClose(function () {
    echo "connection is closed!" . PHP_EOL;
});

// use suspension
$suspension = EventLoop::getSuspension();

EventLoop::repeat(5, weakClosure(function () use ($connection, $suspension) {
    $pingMessage = json_encode([
        'msg_type' => 'ping',
        'timestamp' => microtime(true),
    ]);

    echo "sending ping: {$pingMessage}" . PHP_EOL;
    try {
        $connection->sendText($pingMessage);
    } catch (\Exception $e) {
        echo "send ping failed! " . $e->getMessage() . PHP_EOL;
    }

    // use suspension
    $suspension->resume();
}));

EventLoop::repeat(1, weakClosure(function () use ($connection, $suspension) {
    if ($message = $connection->receive()) {
        $payload = $message->buffer();

        echo "Received: {$payload}" . PHP_EOL;

        $message = json_decode($payload, true);

        if ($message['msg_type'] == 'ping') {
            $pongMessage = json_encode([
                'msg_type' => 'pong',
                'timestamp' => $message['timestamp'],
            ]);

            echo "send pong: {$pongMessage}" . PHP_EOL;
            try {
                $connection->sendText($pongMessage);
            } catch (\Exception $e) {
                echo "send pong failed! " . $e->getMessage() . PHP_EOL;
            }
        }
    }

    // use suspension
    $suspension->resume();
}));

// use suspension in endless while loop
while (1) {
    $suspension->suspend();
}

// don't understand why it is not a preferred way of doing things
//EventLoop::run();

[bwoebi]

EventLoop::run() is perfectly fine when you have no specific top-level event to wait on, i.e. if your code is just repeats.

A common alternative to just using EventLoop::run() here would be using Amp\trapSignal() on SIGINT and do some cleanup afterwards.

[crimson273]

thanks for the tip.

the other thing I can't understand is the proper way of expecting new messages to be received. The approach I used in the example below is workable but this limits me to getting new messages only once per second. What would be the right approach to get new messages immediately once they are received on the client side?

[bwoebi]

The proper way would be to just do a top-level loop (I.e. outside of EventLoop:: and not call EventLoop::run - the receive() call keeps the event loop alive):

    while ($message = $connection->receive()) {
        $payload = $message->buffer();

        echo "Received: {$payload}" . PHP_EOL;

        $message = json_decode($payload, true);

        if ($message['msg_type'] == 'ping') {
            $pongMessage = json_encode([
                'msg_type' => 'pong',
                'timestamp' => $message['timestamp'],
            ]);

            echo "send pong: {$pongMessage}" . PHP_EOL;
            try {
                $connection->sendText($pongMessage);
            } catch (\Exception $e) {
                echo "send pong failed! " . $e->getMessage() . PHP_EOL;
            }
        }
    }

[crimson273]

such approach doesn't trigger the onClose for some reason. No matter what closed the connection - neither the server I am connecting to nor the scirpt itself through the delayed $connection->close(); This still leaves me feeling like I am walking through a maze. Although now I understand how my initial while loop was incorrect, I still do not understand how this is related for triggering (or not triggering) the EventLoop::repeat() and $connection->onClose()

<?php

require dirname(__DIR__) . '/vendor/autoload.php';

use Revolt\EventLoop;
use function Amp\Websocket\Client\connect;

$serverUrl = 'ws://dev.sportlevel.com/highway';

$connection = connect($serverUrl);

$connection->onClose(function () {
    echo "connection is closed!" . PHP_EOL;
});

EventLoop::repeat(5, function () use ($connection) {
    $pingMessage = json_encode([
        'msg_type' => 'ping',
        'timestamp' => microtime(true),
    ]);

    echo "sending ping: {$pingMessage}" . PHP_EOL;
    try {
        $connection->sendText($pingMessage);
    } catch (\Exception $e) {
        echo "send ping failed! " . $e->getMessage() . PHP_EOL;
    }
});

EventLoop::delay(30, function () use ($connection) {
    $connection->close();
});

while ($message = $connection->receive()) {
    $payload = $message->buffer();

    echo "Received: {$payload}" . PHP_EOL;

    $message = json_decode($payload, true);

    if ($message['msg_type'] == 'ping') {
        $pongMessage = json_encode([
            'msg_type' => 'pong',
            'timestamp' => $message['timestamp'],
        ]);

        echo "send pong: {$pongMessage}" . PHP_EOL;
        try {
            $connection->sendText($pongMessage);
        } catch (\Exception $e) {
            echo "send pong failed! " . $e->getMessage() . PHP_EOL;
        }
    }
}

[kelunik]

I'm on mobile right now, so can't test this, but try putting EventLoop::run() at the end. I think the onClose is queued, but not executed, because your script ends at that point.

[korobkovandrey]

//...
$deferred = new Amp\DeferredFuture;
$connection->onClose(function () use ($deferred) {
    echo "connection is closed!" . PHP_EOL;
    $deferred->complete();
});
//...
while ($message = $connection->receive()) {
//...
}
$deferred->getFuture()->await();

[kelunik]

I can reproduce the onClose callback not being executed, exactly how I assumed, because it is queued in the event loop, but the event loop isn't re-entered.

<?php

require dirname(__DIR__) . '/vendor/autoload.php';

use Amp\Websocket\Client\WebsocketHandshake;
use Revolt\EventLoop;
use function Amp\Websocket\Client\connect;

$serverUrl = 'wss://libwebsockets.org';

$handshake = (new WebsocketHandshake('wss://libwebsockets.org'))
    ->withHeader('Sec-WebSocket-Protocol', 'dumb-increment-protocol');

$connection = connect($handshake);

EventLoop::delay(5, function () use ($connection) {
    $connection->close();
});

$connection->onClose(fn () => print 'closed');

while ($message = $connection->receive()) {
    $payload = $message->buffer();

    print $payload;
}

// Remove this call to reproduce the initial report
EventLoop::run();