HcsMessageService API Reference

This document provides a detailed API reference for the HcsMessageService class — a service for submitting and querying messages in Hedera Consensus Service (HCS) topics.

Constructor

constructor

constructor(client: Client, cache?: CacheConfig | Cache | HcsCacheService)

Creates a new instance of HcsMessageService.

Parameters

  • client (required): Hedera SDK client instance used for HCS operations.

  • cache (optional): Cache configuration, cache instance, or an existing HcsCacheService.

Methods

submitMessage

async submitMessage(props: SubmitMessageProps): Promise<SubmitMessageResult>

Submits a message to an HCS topic.

Parameters

  • props (required): Properties for submitting the message.

SubmitMessageProps fields:

  • topicId (string, required): The ID of the topic to which the message will be submitted.

  • message (string, required): The message content to submit.

  • submitKey (PrivateKey, optional): Private key used to sign the submission transaction.

  • waitForChangesVisibility (boolean, optional): If true, waits until the message becomes visible/confirmed in the topic.

  • waitForChangesVisibilityTimeoutMs (number, optional): Timeout in milliseconds to wait for visibility confirmation.

Returns

  • A promise resolving to a SubmitMessageResult object.

SubmitMessageResult fields:

  • nodeId (string): The ID of the node that processed the transaction.

  • transactionId (string): The ID of the transaction.

  • transactionHash (Uint8Array): The cryptographic hash of the transaction.

Throws

  • Error if the message submission transaction fails.

getTopicMessages

async getTopicMessages(props: GetTopicMessagesProps): Promise<TopicMessageData[]>

Retrieves messages from an HCS topic.

Parameters

  • props (required): Properties to configure the message retrieval.

GetTopicMessagesProps fields:

  • topicId (string, required): The ID of the topic to fetch messages from.

  • maxWaitSeconds (number, optional): Maximum number of seconds to wait for new messages during polling.

  • toDate (Date, optional): Upper time bound (inclusive) for message retrieval.

  • limit (number, optional): Maximum number of messages to retrieve.

Returns

  • A promise resolving to an array of TopicMessageData.

TopicMessageData fields:

  • consensusTime (Date): The consensus timestamp when the message was agreed upon.

  • contents (Uint8Array): The raw content of the message.

See Also

HcsMessageService Developer Guide