How to detect client disconnection on PHP socket listener?

Question

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

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;
}

Answer 2

使用get_last_error（）来检查这一点。