rtu.php

<?php

use ModbusTcpClient\Network\BinaryStreamConnection;
use ModbusTcpClient\Packet\ModbusFunction\ReadHoldingRegistersRequest;
use ModbusTcpClient\Packet\RtuConverter;
use ModbusTcpClient\Utils\Packet;

require __DIR__ . '/../vendor/autoload.php';
require __DIR__ . '/logger.php';

$connection = BinaryStreamConnection::getBuilder()
    ->setPort(502)
    ->setHost('127.0.0.1')
    ->setReadTimeoutSec(3) // increase read timeout to 3 seconds
    ->setIsCompleteCallback(function ($binaryData, $streamIndex) {
        return Packet::isCompleteLengthRTU($binaryData);
    })
    ->setLogger(new EchoLogger())
    ->build();

$startAddress = 256;
$quantity = 6;
$slaveId = 1; // RTU packet slave id equivalent is Modbus TCP unitId

$tcpPacket = new ReadHoldingRegistersRequest($startAddress, $quantity, $slaveId);
$rtuPacket = RtuConverter::toRtu($tcpPacket);

try {
    $binaryData = $connection->connect()->sendAndReceive($rtuPacket);
    echo 'RTU Binary received (in hex):   ' . unpack('H*', $binaryData)[1] . PHP_EOL;

    $response = RtuConverter::fromRtu($binaryData);
    echo 'Parsed packet (in hex):     ' . $response->toHex() . PHP_EOL;
    echo 'Data parsed from packet (bytes):' . PHP_EOL;
    print_r($response->getData());

} catch (Exception $exception) {
    echo 'An exception occurred' . PHP_EOL;
    echo $exception->getMessage() . PHP_EOL;
    echo $exception->getTraceAsString() . PHP_EOL;
} finally {
    $connection->close();
}