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Subscribe to a multicast group

A complete worker that joins a multicast group, decodes two writers, and prints their fields — with clean shutdown.

A runnable worker: join 239.0.0.1:4840, accept two DataSetWriters from one publisher, and print each field. SIGTERM stops the loop cleanly.

php worker.php

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

use PhpOpcua\Client\ExtTransportPubSub\SubscriberBuilder;
use PhpOpcua\Client\ExtTransportPubSub\Transport\UdpOptions;
use PhpOpcua\Client\ExtTransportPubSub\Types\DataSetMessage;
use PhpOpcua\Client\ExtTransportPubSub\Types\DataSetMetaData;
use PhpOpcua\Client\ExtTransportPubSub\Types\DataSetReaderConfig;

$meta = DataSetMetaData::fromJsonFile('/etc/opcua/line1.json');

$subscriber = SubscriberBuilder::create()
    ->onDataSetMessage(function (
        DataSetMessage $message,
        int|string $publisherId,
        int $writerGroupId,
    ): void {
        $line = "[w{$message->dataSetWriterId}] ";
        foreach ($message->fields as $field) {
            $line .= "{$field->name}={$field->getScalar()} ";
        }
        echo $line . PHP_EOL;
    })
    ->listenUdp(
        endpoint: 'opc.udp://239.0.0.1:4840',
        transport: new UdpOptions(
            interface: '10.0.0.5',      // scope membership to one NIC
            receiveBufferSize: 262144,  // headroom for bursts
        ),
        readers: [
            new DataSetReaderConfig(100, 1, 1, $meta),   // writer 1
            new DataSetReaderConfig(100, 1, 2, $meta),   // writer 2
        ],
    );

// Clean shutdown between polls
pcntl_async_signals(true);
pcntl_signal(SIGTERM, fn () => $subscriber->stop());
pcntl_signal(SIGINT,  fn () => $subscriber->stop());

$subscriber->run();
echo "stopped\n";

Notes

Scope multicast to a NIC. On a multi-homed host, set UdpOptions::$interface to the address that should receive the group, otherwise membership is joined on 0.0.0.0.
One group, many writers. Both readers share the same metadata here; give each its own DataSetMetaData if the writers carry different DataSets.
Drop nothing silently in dev. While bringing a publisher up, attach a PSR-14 dispatcher and watch MessageDecodeError — a reader-key or metadata mismatch shows up there.

Custom loop instead of run()

Swap run() for a poll() loop if you already have a scheduler:

while ($keepGoing) {
    $subscriber->poll(timeoutMs: 200);   // returns the DataSetMessages decoded
    // …your periodic work…
}

Last updated · 2026-06-09

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