PHP Socket Transfer

SocketTransfer.php

<?php
class SocketTransfer {
    private $sock;
    private $client;
    private $publicKey;
    private $privateKey;
    private $verbose;

    public function __construct($host, $port, $publicKeyPath, $privateKeyPath, $verbose = false) {
        $this->publicKey = file_get_contents($publicKeyPath);
        $this->privateKey = openssl_pkey_get_private(file_get_contents($privateKeyPath));

        $this->sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP) or $this->logError("Could not create socket");
        socket_bind($this->sock, $host, $port) or $this->logError("Could not bind to socket");
        socket_listen($this->sock) or $this->logError("Could not set up socket listener");

        $this->verbose = $verbose;
    }

    public function logError($message) {
        error_log($message);
        if ($this->verbose) {
            echo $message . "\n";
        }
        exit(1);
    }

    public function sendFile($filePath) {
        $fileData = file_get_contents($filePath);
        $symmetricKey = openssl_random_pseudo_bytes(32);

        if (!openssl_public_encrypt($symmetricKey, $encryptedSymmetricKey, $this->publicKey)) {
            $this->logError('Failed to encrypt symmetric key');
        }

        $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-cbc'));
        $encryptedData = openssl_encrypt($fileData, 'aes-256-cbc', $symmetricKey, 0, $iv);
        $toSend = $iv . $encryptedSymmetricKey . $encryptedData;

        for ($i = 0; $i < strlen($toSend); $i += 1024) {
            $chunk = substr($toSend, $i, 1024);
            if (@socket_write($this->client, $chunk, strlen($chunk)) === false) {
                $this->logError('Failed to send data: ' . socket_strerror(socket_last_error()));
            }
        }
    }

    public function receiveFile($outputPath) {
        $received = "";
        while ($chunk = @socket_read($this->client, 1024)) {
            $received .= $chunk;
        }

        $iv = substr($received, 0, 16);
        $encryptedSymmetricKey = substr($received, 16, 256);
        $encryptedData = substr($received, 272);

        if (!openssl_private_decrypt($encryptedSymmetricKey, $symmetricKey, $this->privateKey)) {
            $this->logError("Failed to decrypt symmetric key");
        }

        $decryptedData = openssl_decrypt($encryptedData, 'aes-256-cbc', $symmetricKey, 0, $iv);
        if (file_put_contents($outputPath, $decryptedData) === false) {
            $this->logError("Failed to write file");
        }
    }

    public function acceptConnection() {
        $this->client = socket_accept($this->sock) or $this->logError("Could not accept connection");
    }

    public function closeConnection() {
        socket_close($this->client);
    }

    public function __destruct() {
        socket_close($this->sock);
    }
}