Get topic messages - Hedera

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

The SDK uses the Hedera Consensus Service gRPC APIs provided by the mirror node to perform this function for free.

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(<client, onNext)`	SubscriptionHandle	Client, Consumer<TopicMessage>	Required

//Create the query
new TopicMessageQuery()
    .setTopicId(newTopicId)
    .subscribe(client, topicMessage -> {
        System.out.println("at " + topicMessage.consensusTimestamp + " ( seq = " + topicMessage.sequenceNumber + " ) received topic message of " + topicMessage.contents.length + " bytes");
    });

//v2.0.0

//Create the query
new TopicMessageQuery()
        .setTopicId(topicId)
        .setStartTime(0)
        .subscribe(
            client,
            (message) => console.log(Buffer.from(message.contents, "utf8").toString())
        );
//v2.0.0

//Create the query
_, err = hedera.NewTopicMessageQuery().
    SetTopicID(topicID).
    Subscribe(client, func(message hedera.TopicMessage) {
        if string(message.Contents) == content {
        wait = false
    }
})

if err != nil {
    panic(err)
}

//v2.0.0