Simple TCP Chat in plain PHP

simple_tcp_chat.php

<?php

declare(strict_types=1);

/**
 * Simple TCP Chat.
 *
 * @author Thiago Prates <tsprates@gmail.com>
 */
final class SimpleTcpChat
{
    private const MICROSECONDS_REFRESH = 50000;
    private const EXIT_COMMAND = '/exit';

    private $host;
    private $port;
    private $server;
    private $connections;
    private $cache;

    public function __construct(string $host, int $port)
    {
        $this->host = $host;
        $this->port = $port;
        $this->connections = [];
        $this->cache = [];

        $this->create();
    }

    public function __destruct()
    {
        if (is_resource($this->server)) {
            fclose($this->server);
        }
    }

    public function run(): void
    {
        $this->addConnection($this->server);

        for (;;) {
            $reads = $this->connections;

            if (stream_select($reads, $writes, $excepts, 0, self::MICROSECONDS_REFRESH) !== false) {
                foreach ($reads as $index => $connection) {
                    if ($this->isServer($index)) {
                        $this->handleNewConnection();
                        continue;
                    }

                    if ($this->isLeaving($connection, $index)) {
                        $this->broadcastLeaveChat($connection);
                        $this->removeConnectionByIndex($index);
                        continue;
                    }

                    $data = fgets($connection);

                    $this->putCache($index, $data);

                    if ($this->canSendMessage($data, $index)) {
                        $message = sprintf("%s said: %s", $this->getName($connection), $this->cache($index));
                        $this->broadcast($message);
                        $this->removeCache($index);
                    }
                }
            }
        }
    }

    private function create(): void
    {
        print "Running server on port $this->port" . PHP_EOL;

        $address = sprintf("tcp://%s:%d", $this->host, $this->port);
        $this->server = @stream_socket_server($address, $errorCode, $errorMessage);

        if (!is_resource($this->server)) {
            throw new InvalidArgumentException($errorMessage);
        }

        stream_set_blocking($this->server, false);
    }

    private function handleNewConnection(): void
    {
        if (($newConnection = @stream_socket_accept($this->server, 0, $peerName)) !== false) {
            stream_set_blocking($newConnection, false);
            $this->addConnection($newConnection);
            $this->broadcastWelcome($peerName);
        }
    }

    private function isLeaving($connection, int $index): bool
    {
        return $this->isClosed($connection) || $this->hasRequestToExit($index);
    }

    private function canSendMessage(string $data, int $index): bool
    {
        return $this->isEnterCode($data) && !$this->isEmptyCache($index);
    }

    private function addConnection($connection): void
    {
        $this->connections[(int)$connection] = $connection;
    }

    private function removeConnectionByIndex(int $index): void
    {
        if (isset($this->connections[$index])) {
            fclose($this->connections[$index]);
            unset($this->connections[$index]);
        }
    }

    private function isServer(int $index): bool
    {
        return $index === (int)$this->server;
    }

    private function broadcastWelcome(string $peerName): void
    {
        $message = sprintf('Welcome: %s', $peerName);
        $this->broadcast($message);
    }

    private function broadcast(string $message): void
    {
        print $message . PHP_EOL;

        foreach ($this->connections as $index => $connection) {
            if (!$this->isServer($index)) {
                fwrite($connection, trim($message) . PHP_EOL);
            }
        }
    }

    private function isClosed($connection): bool
    {
        return feof($connection);
    }

    private function hasRequestToExit(int $index): bool
    {
        return !empty($this->cache[$index]) && strtolower(trim($this->cache[$index])) === self::EXIT_COMMAND;
    }

    private function broadcastLeaveChat($connection): void
    {
        $message = sprintf("%s has left.", $this->getName($connection));

        $this->broadcast($message);
    }

    private function getName($connection)
    {
        return stream_socket_get_name($connection, true);
    }

    private function putCache(int $index, string $data): void
    {
        $this->cache[$index] = $this->cache($index) . $data;
    }

    private function isEnterCode(string $str): bool
    {
        return $str === PHP_EOL;
    }

    private function isEmptyCache(int $index): bool
    {
        return empty(trim($this->cache($index)));
    }

    private function cache(int $index): string
    {
        return $this->cache[$index] ?? '';
    }

    private function removeCache(int $index): void
    {
        unset($this->cache[$index]);
    }
}

// Example: How to use
$chat = new SimpleTcpChat('0.0.0.0', 9000);
$chat->run();