FC6 WriteSingleRegisterRequest Error

[nickblack777]

Testing the WriteSingleRegisterRequest function. It gives an error when connecting:

Packet to be sent (in hex): 64d200000006000600010037 An exception occurred fread error during receiveFrom #0

Here is my code(I have hidden the IP in setHost. He is static):

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

use ModbusTcpClient\Network\BinaryStreamConnection;
use ModbusTcpClient\Packet\ModbusFunction\WriteSingleRegisterRequest;
use ModbusTcpClient\Packet\ModbusFunction\WriteSingleRegisterResponse;
use ModbusTcpClient\Packet\ResponseFactory;


$connection = BinaryStreamConnection::getBuilder()
    ->setPort(502)
    ->setHost('127.0.0.1')
    ->build();

$startAddress = 1;
$value = 55;
$packet = new WriteSingleRegisterRequest($startAddress, $value);
echo 'Packet to be sent (in hex): ' . $packet->toHex() . PHP_EOL;


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

    /* @var $response WriteSingleRegisterResponse */
    $response = ResponseFactory::parseResponseOrThrow($binaryData);
    echo 'Parsed packet (in hex):     ' . $response->toHex() . PHP_EOL;
    echo 'Register value parsed from packet:' . PHP_EOL;
    print_r($response->getWord()->getInt16());

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

When testing via the Modbus Poll program, the value changes without errors.
https://drive.google.com/file/d/1VlH0qBCwPwIqTe2Mni437SOelCWqbX3K/view?usp=drivesdk

Please tell me what could be wrong. Thanks.

[aldas]

Are you sure that your server (where PHP is running) is allowed to connect to that modbus server and port?

[nickblack777]

Yes, I have tested receiving data via examples/index.php I can give you the ip and port of my device - please write where to send it.

[nickblack777]

Or are receiving and sending information different? I use regular virtual hosting. There were no errors while receiving the information.

[aldas]

Try writing with PHP from the same machine you are using Modbus Poll program. Your local machine and virtual hosting and modbus server can have quite different firewalls rules depending from the source/destination.

[nickblack777]

Thanks, I'll try now

[aldas]

and try to add logger to response can be seen

$connection = BinaryStreamConnection::getBuilder()
    ->setPort(5020)
    ->setHost('127.0.0.1')
    ->setLogger(new EchoLogger()) // <-- add logger
    ->build();

[aldas]

Okey I see. From your modpoll picture I see your are using slaveID/unitID = 1 but in you code you are not setting any - thus it will be 0

try

$unitID = 1;
$packet = new WriteSingleRegisterRequest($startAddress, $value, $unitID);

[nickblack777]

In my device, it doesn't matter what the id will be. It defaults to 0. This is not the cause of the error.

[aldas]

mmm, ok, lets go back to that picture - is your server using Modbus RTU (packets with crc) or Modbus TCP?

From that picture I see RTU packet

if this is the case you need to convert TCP to RTU packet. See https://github.com/aldas/modbus-tcp-client/blob/master/examples/rtu.php

[nickblack777]

Modbus TCP

[nickblack777]

RTU is shown there as an example. My device is Siemens Logo. Supports Modbus TCP

[aldas]

You probably need to capture network traffic for both Modpoll and PHP packets sent/received. https://github.com/aldas/modbus-tcp-client/wiki/Debugging-guide and see what are the differences.

[aldas]

These lines are necessary to convert TCP packet to RTU

$rtuPacket = RtuConverter::toRtu($packet);
...
$response = RtuConverter::fromRtu($binaryData);

[nickblack777]

Same error :(

[aldas]

I think you need to capture traffic and see the differences.

The FC6 packet ifself is

modbus-tcp-client/src/Packet/ModbusFunction/WriteSingleRegisterRequest.php

Lines 18 to 25 in 73eba8b

	* Example packet: \x00\x01\x00\x00\x00\x06\x11\x06\x00\x6B\x01\x01
	* \x00\x01 - transaction id
	* \x00\x00 - protocol id
	* \x00\x06 - number of bytes in the message (PDU = ProtocolDataUnit) to follow
	* \x11 - unit id
	* \x06 - function code
	* \x00\x6B - start address
	* \x01\x01 - register data

In case of RTU the first 6 bytes are not included and there will be 2 extra bytes for CRC at the end.

[aldas]

You had php-fpm.log output. could you paste it again? Or increase error reporting

etc

error_repoerting(E_ALL);  
ini_set('display_errors',1);

[nickblack777]

These are my connection settings. All the same, the connection is TCP, not RTU. You can connect remotely from my device.

[nickblack777]

I don't know what happened, but it worked

[nickblack777]

I disabled the connection via Modbuss Poll and everything worked. I thought the devices support multiple connections at the same time. I will delete messages with my settings.

[aldas]

This is maybe configurable. I have seen WAGO PLCs that cap out at 10 tcp connections but I have seen also NMEA0183 tcp buffers/multiplexers that only allow 1 tcp connection per IP