get-topic-message.md

Get topic messages

Subscribe to a topic ID's messages from a mirror node. You will receive all messages for the specified topic or within the defined start and end time.

Query Fees

• Please see the transaction and query fees table for base transaction fee
• Please use the Hedera fee estimator to estimate your query fee cost

{% tabs %} {% tab title="V1" %}

Constructor	Description
new MirrorConsensusTopicQuery()	Initializes the MirrorConsensusTopicQuery object

new MirrorConsensusTopicQuery()

Methods

Method	Type	Description	Requirement
setTopicId(<topicId>)	TopicId	The topic ID to subscribe to	Required
setStartTime(<startTime>)	Instant	The time to start subscribing to a topic's messages	Optional
setEndTime(<endTime>)	Instant	The time to stop subscribing to a topic's messages	Optional
setLimit(<limit>)	long	The number of messages to return	Optional
subscribe(<mirrorClient, onNext onError)	MirrorClient, Consumer <MirrorConsensusTopicResponse>, Consumer<Throwable>	Subscribe and get the messages for a topic	Required

{% code title="Java" %}

new MirrorConsensusTopicQuery()
    .setTopicId(topicId)
    .subscribe(mirrorClient, resp -> {
                String messageAsString = new String(resp.message, StandardCharsets.UTF_8);

                System.out.println(resp.consensusTimestamp + " received topic message: " + messageAsString);
            },
            // On gRPC error, print the stack trace
            Throwable::printStackTrace);
//v1.3.2

{% endcode %}

{% code title="JavaScript" %}

new MirrorConsensusTopicQuery()
    .setTopicId(topicId)
    .subscribe(
        consensusClient,
        (message) => console.log(message.toString()),
        (error) => console.log(`Error: ${error}`)
    );

{% endcode %} {% endtab %} {% endtabs %}