CODEWITHSUNDEEP
phpsocketstcpstream
Rupert
Rupert

Reputation: 2159

How can I detect when a stream client is no longer available in PHP (eg network cable pulled out)

Is there any way (other than checking for ping responses) to detect when a client stream (I don't know if a stream would be any different from sockets) becomes unavailable (ie there is no longer any connection but no clean disconnection was made)?

Using this code:

#!/usr/bin/env php
<?php
$socket = stream_socket_server(
    'tcp://192.168.1.1:47700',
    $errno,
    $errstr,
    STREAM_SERVER_BIND|STREAM_SERVER_LISTEN,
    stream_context_create(
        array(),
        array()
    )
);
if (!$socket) {
    echo 'Could not listen on socket'."\n";
}
else {
    $clients = array((int)$socket => $socket);
    $last = time();
    while(true) {
        $read = $clients;
        $write = null;
        $ex = null;
        stream_select(
            $read,
            $write,
            $ex,
            5
        );
        foreach ($read as $sock) {
            if ($sock === $socket) {
                echo 'Incoming on master...'."\n";
                $client = stream_socket_accept(
                    $socket,
                    5
                );
                if ($client) {
                    stream_set_timeout($client, 1);
                    $clients[(int)$client] = $client;
                }
            }
            else {
                echo 'Incoming on client '.((int)$sock)."...\n";
                $length = 1400;
                $remaining = $length;

                $buffer = '';
                $metadata['unread_bytes'] = 0;
                do {
                    if (feof($sock)) {
                        break;
                    }

                    $result = fread($sock, $length);

                    if ($result === false) {
                        break;
                    }

                    $buffer .= $result;

                    if (feof($sock)) {
                        break;
                    }

                    $continue = false;

                    if (strlen($result) == $length) {
                        $continue = true;
                    }

                    $metadata = stream_get_meta_data($sock);
                    if ($metadata && isset($metadata['unread_bytes']) && $metadata['unread_bytes']) {
                        $continue = true;
                        $length = $metadata['unread_bytes'];
                    }
                } while ($continue);

                if (strlen($buffer) === 0 || $buffer === false) {
                    echo 'Client disconnected...'."\n";
                    stream_socket_shutdown($sock, STREAM_SHUT_RDWR);
                    unset($clients[(int)$sock]);
                }
                else {
                    echo 'Received: '.$buffer."\n";
                }
                echo 'There are '.(count($clients) - 1).' clients'."\n";
            }

        }
        if ($last < (time() - 5)) {
            foreach ($clients as $id => $client) {
                if ($client !== $socket) {
                    $text = 'Yippee!';
                    $ret = fwrite($client, $text);
                    if ($ret !== strlen($text)) {
                        echo 'There seemed to be an error sending to the client'."\n";
                    }
                }
            }
        }
    }
}
if ($socket) {
    stream_socket_shutdown($socket, STREAM_SHUT_RDWR);
}

and a sockets client on a different computer, I can connect to the server, send and receive data, and disconnect cleanly and everything functions as expected. If, however, I pull the network connection on the client computer, nothing is detected on the server side - the server keeps on listening to the client socket, and also writes to it without any error manifesting itself.

Upvotes: 3

Views: 3476

Answers (2)

Diggy Dude
Diggy Dude

Reputation: 19

As I understand it, calling feof($stream) will tell you if the remote socket disconnected, but I'm not absolutely certain about that. I'm using ping/pong myself while continuing to research a solution.

Upvotes: 1

Filippos Karapetis
Filippos Karapetis

Reputation: 4652

You need to set a socket timeout, in which case you get an error if a client does not respond in a timely fashion.

Check PHP's stream_set_timeout function: http://www.php.net/manual/en/function.stream-set-timeout.php

Also check socket_set_option: http://php.net/manual/en/function.socket-set-option.php

and finally, check out this great article on how to use sockets in PHP effectively: "PHP Socket Programming, done the Right Way™" http://christophh.net/2012/07/24/php-socket-programming/

Upvotes: 0

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