How to detect client disconnection on PHP socket listener?

Question

Hi all,

I've been testing PHP socket listening, and ran into the aforementioned problem. My test listener works otherwise fine, but if a client disconnects without telling the server, the script goes into and infinite loop until a new client connects. The problem seems to be on line $ready = socket_select($read, $write = NULL, $except = NULL, $tv_sec = NULL); since it should stop to wait for connections here, but instead it skips the wait and runs straight through the loop.

Any pointers would be appreciated.

Code:

#!/usr/bin/php -q
<?php

$debug = true;
function e($str) {
    global $debug;
    if($debug) { echo($str . "\n"); }
}

e("Starting...");
error_reporting(1);
ini_set('display_errors', '1');

e("Creating master socket...");
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
$max_clients = 10;

e("Setting socket options...");
socket_set_option($socket, SOL_SOCKET, SO_REUSEADDR, 1);
e("Binding socket...");
socket_bind($socket, "192.168.1.38", 20000);
e("Listening...");
socket_listen($socket, $max_clients);

$clients = array('0' => array('socket' => $socket));

while(TRUE) {
    e("Beginning of WHILE");
    $read[0] = $socket;

    for($i=1; $i<count($clients)+1; ++$i) {
        if($clients[$i] != NULL) {
            $read[$i+1] = $clients[$i]['socket'];
        }
    }

    e("Selecting socket...");
    $ready = socket_select($read, $write = NULL, $except = NULL, $tv_sec = NULL);
    e("socket_select returned " . $ready);
    e("If...");
    var_dump($socket);
    var_dump($read);
    if(in_array($socket, $read)) {
        e("If OK");
        for($i=1; $i < $max_clients+1; ++$i) {
            if(!isset($clients[$i])) {
                e("Accepting connection...");
                $clients[$i]['socket'] = socket_accept($socket);

                socket_getpeername($clients[$i]['socket'],$ip);
                e("Peer: " . $ip);
                $clients[$i]['ipaddr'] = $ip;

                socket_write($clients[$i]['socket'], 'Welcome to my Custom Socket Server'."\r\n");
                socket_write($clients[$i]['socket'], 'There are '.(count($clients) - 1).' client(s) connected to this server.'."\r\n");

                echo 'New client connected: ' . $clients[$i]['ipaddr'] .' ';
                break;
            } elseif($i == $max_clients - 1) {
                echo 'Too many Clients connected!'."\r\n";
            }

            if(--$ready <= 0) {
                continue;
            } 
        }
    }

    e("For...");
    for($i=1; $i<$max_clients+1; ++$i) {
        e("In...");
        if(in_array($clients[$i]['socket'], $read)) {
            e("Reading data...");
            $data = @socket_read($clients[$i]['socket'], 1024, PHP_NORMAL_READ);

            if($data === FALSE) {
                unset($clients[$i]);
                echo 'Client disconnected!',"\r\n";
                continue;
            }

            $data = trim($data);

            if(!empty($data)) {
                if($data == 'exit') {
                    socket_write($clients[$i]['socket'], 'Thanks for trying my Custom Socket Server, goodbye.'."\n");
                    echo 'Client ',$i,' is exiting.',"\n";
                    socket_close($clients[$i]['socket']);
                    unset($clients[$i]);
                    continue;
                } 

                for($j=1; $j<$max_clients+1; ++$j) {
                    if(isset($clients[$j]['socket'])) {
                        if(($clients[$j]['socket'] != $clients[$i]['socket']) && ($clients[$j]['socket'] != $socket)) {
                            echo($clients[$i]['ipaddr'] . ' is sending a message!'."\r\n");
                            socket_write($clients[$j]['socket'], '[' . $clients[$i]['ipaddr'] . '] says: ' . $data . "\r\n");
                        }
                    }
                }
                break;
            }
        }
    }
    if($loops == 0) {
        $firstloop = time();
        $loops++;
    } else {
        $loops++;
        if((time() - $firstloop) >= 5 && $loops > 25) {
            /*for($j=1; $j<$max_clients+1; ++$j) {
                if(isset($clients[$j]['socket'])) {
                    if($clients[$j]['socket'] != $socket) {
                        echo('Server is looping, sending keepalive...'."\r\n");
                        if(!socket_write($clients[$j]['socket'], '-KEEPALIVE-' . "\r\n")) {
                            echo 'Client ',$j,' not found, killing...',"\n";
                            socket_close($clients[$j]['socket']);
                            unset($clients[$j]);
                            die("debug");
                        }
                    }
                }
            }*/
            die("Looping started.\n");
        }
    }
}
?>

Answer 1

Use get_last_error() to check this.

Answer 2

Found out what the problem was, I was missing a socket_close() from the "Client disconnected" block. So the correct block is:

if($data === FALSE) {
    socket_close($clients[$i]['socket']);
    unset($clients[$i]);
    echo 'Client disconnected!',"\r\n";
    continue;
}