Docs · API

Modules

PubSubModule is the in-process extension point: hook custom behaviour into the kernel for every decoded DataSetMessage, no fork required.

The kernel runs a list of PubSubModules. The built-in DataSetReaderModule does the demux-and-decode; your own modules run alongside it for every decoded DataSetMessage.

`PubSubModule`

Abstract base. Override what you need — both methods have empty defaults.

method · public

returns void

onDataSetMessage(DataSetMessage \$message, int|string \$publisherId, int \$writerGroupId, string \$transportUri): void

Called for every DataSetMessage the kernel decodes, with the demux key and the originating transport URI. Default: no-op.

method · public

returns void

reset(): void

Called to clear any per-run state. Default: no-op.

php a metrics module

use PhpOpcua\Client\ExtTransportPubSub\Module\PubSubModule;
use PhpOpcua\Client\ExtTransportPubSub\Types\DataSetMessage;

final class CountByWriter extends PubSubModule
{
    /** @var array<int,int> */
    public array $counts = [];

    public function onDataSetMessage(
        DataSetMessage $message,
        int|string $publisherId,
        int $writerGroupId,
        string $transportUri,
    ): void {
        $this->counts[$message->dataSetWriterId] ??= 0;
        $this->counts[$message->dataSetWriterId]++;
    }

    public function reset(): void
    {
        $this->counts = [];
    }
}

$module = new CountByWriter();

SubscriberBuilder::create()
    ->addModule($module)
    ->onDataSetMessage($callback)
    ->listenUdp(endpoint: 'opc.udp://239.0.0.1:4840', readers: [$reader]);

Modules vs callbacks

onDataSetMessage() on the builder registers a plain callback; a module is a stateful object with a lifecycle (reset()). Use a callback for a quick handler, a module when you need to hold state, expose results, or package reusable behaviour.

Built-in module

DataSetReaderModule (constructed from your DataSetReaderConfig[]) is added automatically by the builder. It holds the reader registry the codec uses to decode and demux each datagram, so your modules — and your callbacks — only see DataSetMessages that matched a configured reader.

Last updated · 2026-06-09

Edit on GitHub Report issue

← Previous

Readers & metadata

Events