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Use Composer to install this library as dependency.
composer require aldas/modbus-tcp-client
This library is influenced by phpmodbus library and meant to be provide decoupled Modbus protocol (request/response packets) and networking related features so you could build modbus client with our own choice of networking code (ext_sockets/streams/Reactphp/Amp asynchronous streams) or use library provided networking classes (php Streams)
Applies to multibyte data that are stored in Word/Double/Quad word registers basically everything that is not (u)int16/byte/char.
So if we receive from network 0x12345678 (bytes: ABCD) and want to convert that to a 32 bit register there could be 4 different ways to interpret bytes and word order depending on modbus server architecture and client architecture. NB: TCP, and UDP, are transmitted in big-endian order so we choose this as base for examples
Library supports following byte and word orders:
Default (global) endianess used for parsing can be changed with:
Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
For non-global cases see API methods argument list if method support using custom endianess.
See Endian.php for additional info and Types.php for supported data types.
Modbus is binary protocol which revolves about addresses of Registers/Word (16bit, 2 byte of data) and Coils (1 bit of data). Coils are booleans but Register/Word or multiple Registers can hold different data types. Following is ways to access different data types from Registers:
Most of the for data types have optional arguments for providing Endian type. By default data is parsed as being Big Endian Low Word first endian.
Exaple: getting uint32 value as Little Endian Low Word First
$dword->getUInt32(Endian::LITTLE_ENDIAN | Endian::LOW_WORD_FIRST);
1-16bit data types are hold by Word class which hold 2 bytes of data.
$address = 100;
$word = $response->getWordAt($address);
Following methods exists to get different types out of single Word instance:
boolean - 1bit, true/false, $word->isBitSet(11)
byte - 8bit, 1 byte, range 0 to 255
$word->getHighByteAsInt()
$word->getLowByteAsInt()
uint16 - 16bit, 2 byte, range 0 to 65535 $word->getUInt16()
int16 - 16bit, 2 byte, range -32768 to 32767 $word->getInt16()
and following additional methods:
$word->getBytes() return Words as array of 2 integers (0-255)17-32bit data types are hold by DoubleWord class which hold 4 bytes of data.
$address = 100;
$dword = $response->getDoubleWordAt($address);
Following methods exists to get different types out of single DoubleWord instance:
uint32 - 32bit, 4 bytes, range 0 to 4294967295, $dword->getUInt32()
int32 - 64bit, 8 bytes, range -2147483648 to 2147483647, $dword->getInt32()
float - 64bit, 8 bytes, range -3.4e+38 to 3.4e+38, $dword->getFloat()
and following additional methods:
$dword->getBytes() return DoubleWord as array of 4 integers (0-255)$dword->getHighBytesAsWord() returns first 2 bytes as Word
$dword->getLowBytesAsWord() returns last 2 bytes as Word
64bit data types are hold by QuadWord class which hold 8 bytes of data.
NB: 64-bit PHP supports only up to 63-bit (signed) integers.
$address = 100;
$qword = $response->getQuadWordAt($address);
Following methods exists to get different types out of single QuadWord instance:
uint32 - 64bit, 8 bytes, range 0 to 9223372036854775807, $dword->getUInt64()
int32 - 64bit, 8 bytes, range -9223372036854775808 to 9223372036854775807, $dword->getInt64()
double - 64bit, 8 bytes, range 2.2250738585072e-308 to 1.7976931348623e+308, $dword->getDouble()
and following additional methods:
$qword->getBytes() return QuadWord as array of 8 integers (0-255)$qword->getHighBytesAsDoubleWord() returns first 4 bytes as DoubleWord
$qword->getLowBytesAsDoubleWord() returns last 4 bytes as DoubleWord
ASCII (8bit character) string can be extracted from response as utf-8 string
$address = 20;
$length = 10;
$string = $response->getAsciiStringAt($address, $length);
Some of the Modbus function examples are in examples/ folder
Advanced usage:
Request multiple packets with higher level API:
$address = 'tcp://127.0.0.1:5022';
$unitID = 0; // also known as 'slave ID'
$fc3 = ReadRegistersBuilder::newReadHoldingRegisters($address, $unitID)
->unaddressableRanges([[100,110], [1512]])
->bit(256, 15, 'pump2_feedbackalarm_do')
// will be split into 2 requests as 1 request can return only range of 124 registers max
->int16(657, 'battery3_voltage_wo')
// will be another request as uri is different for subsequent int16 register
->useUri('tcp://127.0.0.1:5023')
->string(
669,
10,
'username_plc2',
function ($value, $address, $response) {
return 'prefix_' . $value; // optional: transform value after extraction
},
function (\Exception $exception, Address $address, $response) {
// optional: callback called then extraction failed with an error
return $address->getType() === Address::TYPE_STRING ? '' : null; // does not make sense but gives you an idea
}
)
->build(); // returns array of 3 ReadHoldingRegistersRequest requests
// this will use PHP non-blocking stream io to recieve responses
$responseContainer = (new NonBlockingClient(['readTimeoutSec' => 0.2]))->sendRequests($fc3);
print_r($responseContainer->getData()); // array of assoc. arrays (keyed by address name)
print_r($responseContainer->getErrors());
Response structure
[
[ 'pump2_feedbackalarm_do' => true, ],
[ 'battery3_voltage_wo' => 12, ],
[ 'username_plc2' => 'prefix_admin', ]
]
Low level - send packets:
$connection = BinaryStreamConnection::getBuilder()
->setHost('192.168.0.1')
->build();
$packet = new ReadHoldingRegistersRequest(256, 8); //create FC3 request packet
try {
$binaryData = $connection->connect()->sendAndReceive($packet);
//parse binary data to response object
$response = ResponseFactory::parseResponseOrThrow($binaryData);
//same as 'foreach ($response->getWords() as $word) {'
foreach ($response as $word) {
print_r($word->getInt16());
}
// print registers as double words in big endian low word first order (as WAGO-750 does)
foreach ($response->getDoubleWords() as $dword) {
print_r($dword->getInt32(Endian::BIG_ENDIAN_LOW_WORD_FIRST));
}
// set internal index to match start address to simplify array access
$responseWithStartAddress = $response->withStartAddress(256);
print_r($responseWithStartAddress[256]->getBytes()); // use array access to get word
print_r($responseWithStartAddress->getDoubleWordAt(257)->getFloat());
} catch (Exception $exception) {
echo $exception->getMessage() . PHP_EOL;
} finally {
$connection->close();
}
Difference between Modbus RTU and Modbus TCP is that:
See http://www.simplymodbus.ca/TCP.htm for more detailsed explanation
This library was/is originally meant for Modbus TCP but it has support to convert packet to RTU and from RTU. See this examples/rtu.php for example.
$rtuBinaryPacket = RtuConverter::toRtu(new ReadHoldingRegistersRequest($startAddress, $quantity, $slaveId));
$binaryData = $connection->connect()->sendAndReceive($rtuBinaryPacket);
$responseAsTcpPacket = RtuConverter::fromRtu($binaryData);
See Linux example in 'examples/rtu_usb_to_serial.php'
See example in 'examples/rtu_over_tcp_with_higherlevel_api.php'
Examples folder has index.php which can be used with php built-in web server to test out communication with our own PLCs.
git clone https://github.com/aldas/modbus-tcp-client.git
cd modbus-tcp-client
composer install
php -S localhost:8080 -t examples/
Now open http://localhost:8080 in browser. See additional query parameters from index.php.
See CHANGELOG.md
composer test
composer test-unit
composer test-integration
For Windows users:
vendor/bin/phpunit
vendor/bin/phpunit --testsuite 'unit-tests'
vendor/bin/phpunit --testsuite 'integration-tests'
Run PHPStan analysis compose check
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