Submit Message to Private Topic
In the previous tutorial "Submit Your First Message", you have learned how to submit a message to a public topic. It means anyone can send a message to the topic you created because you didn't set a Submit Key.
When setting a Submit Key, your topic becomes a private topic because each message needs to be signed by the Submit Key. Therefore, you can control who can submit messages to your topic.
We recommend you complete the "Submit Your First Message" tutorial to get a basic understanding of the Hedera Consensus Service. This example does not build upon the previous examples.
To create a private topic, you will use
setSubmitKey() to set a Submit Key. This key needs to sign all messages someone sends to the topic. A message will be rejected if you don't sign the message or sign with an incorrect key. The cost of creating a private topic is the same as a public topic: $0.01.Java
JavaScript
Go
// Create a new topic
TransactionResponse txResponse = new TopicCreateTransaction()
.setSubmitKey(myPrivateKey.getPublicKey())
.execute(client);
// Get the receipt
TransactionReceipt receipt = txResponse.getReceipt(client);
// Get the topic ID
TopicId topicId = receipt.topicId;
// Log the topic ID
System.out.println("Your topic ID is: " +topicId);
// Wait 5 seconds between consensus topic creation and subscription creation
Thread.sleep(5000);
// Create a new topic
let txResponse = await new TopicCreateTransaction()
.setSubmitKey(myPrivateKey.publicKey)
.execute(client);
// Grab the newly generated topic ID
let receipt = await txResponse.getReceipt(client);
console.log(`Your topic ID is: ${receipt.topicId}`);
// Wait 5 seconds between consensus topic creation and subscription creation
await new Promise((resolve) => setTimeout(resolve, 5000));
// Create a new topic
transactionResponse, err := hedera.NewTopicCreateTransaction().
SetSubmitKey(myPrivateKey.PublicKey()).
Execute(client)
if err != nil {
println(err.Error(), ": error creating topic")
return
}
// Get the topic create transaction receipt
transactionReceipt, err := transactionResponse.GetReceipt(client)
if err != nil {
println(err.Error(), ": error getting topic create receipt")
return
}
// Get the topic ID from the transaction receipt
topicID := *transactionReceipt.TopicID
//Log the topic ID to the console
fmt.Printf("topicID: %v\n", topicID)
The code used to subscribe to a public or private topic doesn't change. Anyone can listen to the messages you send to your private topic. You need to provide the
TopicMessageQuery() with your topic ID to subscribe to it. Java
JavaScript
Go
// Subscribe to the topic
new TopicMessageQuery()
.setTopicId(topicId)
.subscribe(client, resp -> {
String messageAsString = new String(resp.contents, StandardCharsets.UTF_8);
System.out.println(resp.consensusTimestamp + " received topic message: " + messageAsString);
});
// Subscribe to the topic
new TopicMessageQuery()
.setTopicId(topicId)
.subscribe(client, null, (message) => {
let messageAsString = Buffer.from(message.contents, "utf8").toString();
console.log(
`${message.consensusTimestamp.toDate()} Received: ${messageAsString}`
);
});
// Subscribe to the topic
_, err = hedera.NewTopicMessageQuery().
SetTopicID(topicID).
Subscribe(client, func(message hedera.TopicMessage) {
fmt.Println(message.ConsensusTimestamp.String(), "received topic message ", string(message.Contents), "\r")
})
Now you are ready to submit a message to your private topic. To do this, you will use
TopicMessageSubmitTransaction(). However, you need to sign this transaction with your Submit Key. The cost for sending a message to a private topic is the same as a public topic: $0.0001. Java
JavaScript
Go
// Send message to private topic
TransactionResponse submitMessage = new TopicMessageSubmitTransaction()
.setTopicId(topicId)
.setMessage("Submitkey set!")
.freezeWith(client)
.sign(myPrivateKey)
.execute(client)
// Get the receipt of the transaction
TransactionReceipt receipt2 = submitMessage.getReceipt(client);
// Prevent the main thread from exiting so the topic message can be returned and printed to the console
Thread.sleep(30000);
// Send message to private topic
let submitMsgTx = await new TopicMessageSubmitTransaction({
topicId: topicId,
message: "Submitkey set!",
})
.freezeWith(client)
.sign(myPrivateKey);
let submitMsgTxSubmit = await submitMsgTx.execute(client);
// Get the receipt of the transaction
let getReceipt = await submitMsgTxSubmit.getReceipt(client);
// Get the status of the transaction
const transactionStatus = getReceipt.status;
console.log("The message transaction status " + transactionStatus.toString());
// Prepare message to send to private topic
submitMessageTx, err := hedera.NewTopicMessageSubmitTransaction().
SetMessage([]byte("Submitkey set!")).
SetTopicID(topicID).
FreezeWith(client)
if err != nil {
println(err.Error(), ": error freezing topic message submit transaction")
return
}
// Sign message with submit key
submitMessageTx.Sign(myPrivateKey)
// Submit message
submitTxResponse, err := submitMessageTx.Execute(client)
if err != nil {
println(err.Error(), ": error submitting to topic")
return
}
// Get the receipt of the transaction
receipt, err := submitTxResponse.GetReceipt(client)
// Get the transaction status
transactionStatus := receipt.Status
fmt.Println("The message transaction status " + transactionStatus.String())
// Prevent the program from exiting to display the message from the mirror node to the console
time.Sleep(30000)
To conclude: The total cost to create a topic and send a message to it is $0.0101.
import com.hedera.hashgraph.sdk.*;
import io.github.cdimascio.dotenv.Dotenv;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.TimeoutException;
public class CreateTopicTutorial {
public static void main(String[] args) throws TimeoutException, PrecheckStatusException, ReceiptStatusException, InterruptedException {
// Grab your Hedera testnet account ID and private key
AccountId myAccountId = AccountId.fromString(Dotenv.load().get("MY_ACCOUNT_ID"));
PrivateKey myPrivateKey = PrivateKey.fromString(Dotenv.load().get("MY_PRIVATE_KEY"));
// Build your Hedera client
Client client = Client.forTestnet();
client.setOperator(myAccountId, myPrivateKey);
// Create a new topic
TransactionResponse txResponse = new TopicCreateTransaction()
.setSubmitKey(myPrivateKey.getPublicKey())
.execute(client);
// Get the receipt
TransactionReceipt receipt = txResponse.getReceipt(client);
// Get the topic ID
TopicId topicId = receipt.topicId;
// Log the topic ID
System.out.println("Your topic ID is: " +topicId);
// Wait 5 seconds between consensus topic creation and subscription creation
Thread.sleep(5000);
// Subscribe to the topic
new TopicMessageQuery()
.setTopicId(topicId)
.subscribe(client, resp -> {
String messageAsString = new String(resp.contents, StandardCharsets.UTF_8);
System.out.println(resp.consensusTimestamp + " received topic message: " + messageAsString);
});
// Send message to private topic
TransactionResponse submitMessage = new TopicMessageSubmitTransaction()
.setTopicId(topicId)
.setMessage("Submitkey set!")
.freezeWith(client)
.sign(myPrivateKey)
.execute(client)
// Get the receipt of the transaction
TransactionReceipt receipt2 = submitMessage.getReceipt(client);
// Wait before the main thread exits to return the topic message to the console
Thread.sleep(30000);
}
}
console.clear();
require("dotenv").config();
const {
AccountId,
PrivateKey,
Client,
TopicCreateTransaction,
TopicMessageQuery,
TopicMessageSubmitTransaction,
} = require("@hashgraph/sdk");
// Grab the OPERATOR_ID and OPERATOR_KEY from the .env file
const myAccountId = process.env.MY_ACCOUNT_ID;
const myPrivateKey = process.env.MY_PRIVATE_KEY;
// Build Hedera testnet and mirror node client
const client = Client.forTestnet();
// Set the operator account ID and operator private key
client.setOperator(myAccountId, myPrivateKey);
async function main() {
// Create a new topic
let txResponse = await new TopicCreateTransaction()
.setSubmitKey(myPrivateKey.publicKey)
.execute(client);
// Grab the newly generated topic ID
let receipt = await txResponse.getReceipt(client);
let topicId = receipt.topicId;
console.log(`Your topic ID is: ${topicId}`);
// Wait 5 seconds between consensus topic creation and subscription creation
await new Promise((resolve) => setTimeout(resolve, 5000));
// Create the topic
new TopicMessageQuery()
.setTopicId(topicId)
.subscribe(client, null, (message) => {
let messageAsString = Buffer.from(message.contents, "utf8").toString();
console.log(
`${message.consensusTimestamp.toDate()} Received: ${messageAsString}`
);
});
// Send message to private topic
let submitMsgTx = await new TopicMessageSubmitTransaction({
topicId: topicId,
message: "Submitkey set!",
})
.freezeWith(client)
.sign(myPrivateKey);
let submitMsgTxSubmit = await submitMsgTx.execute(client);
let getReceipt = await submitMsgTxSubmit.getReceipt(client);
// Get the status of the transaction
const transactionStatus = getReceipt.status;
console.log("The message transaction status: " + transactionStatus.toString());
}
main();
package main
import (
"fmt"
"os"
"time"
"github.com/hashgraph/hedera-sdk-go/v2"
"github.com/joho/godotenv"
)
func main() {
// Loads the .env file and throws an error if it cannot load the variables from that file corectly
err := godotenv.Load(".env")
if err != nil {
panic(fmt.Errorf("Unable to load enviroment variables from .env file. Error:\n%v\n", err))
}
// Grab your testnet account ID and private key from the .env file
myAccountId, err := hedera.AccountIDFromString(os.Getenv("MY_ACCOUNT_ID"))
if err != nil {
panic(err)
}
myPrivateKey, err := hedera.PrivateKeyFromString(os.Getenv("MY_PRIVATE_KEY"))
if err != nil {
panic(err)
}
// Create your testnet client
client := hedera.ClientForTestnet()
client.SetOperator(myAccountId, myPrivateKey)
// Create a new topic
transactionResponse, err := hedera.NewTopicCreateTransaction().
SetSubmitKey(myPrivateKey.PublicKey()).
Execute(client)
if err != nil {
println(err.Error(), ": error creating topic")
return
}
// Get the topic create transaction receipt
transactionReceipt, err := transactionResponse.GetReceipt(client)
if err != nil {
println(err.Error(), ": error getting topic create receipt")
return
}
// Get the topic ID from the transaction receipt
topicID := *transactionReceipt.TopicID
// Log the topic ID to the console
fmt.Printf("topicID: %v\n", topicID)
//Create the query to subscribe to a topic
_, err = hedera.NewTopicMessageQuery().
SetTopicID(topicID).
Subscribe(client, func(message hedera.TopicMessage) {
fmt.Println(message.ConsensusTimestamp.String(), "received topic message ", string(message.Contents), "\r")
})
// Prepare message to send to private topic
submitMessageTx, err := hedera.NewTopicMessageSubmitTransaction().
SetMessage([]byte("Submitkey set!")).
SetTopicID(topicID).
FreezeWith(client)
if err != nil {
println(err.Error(), ": error freezing topic message submit transaction")
return
}
// Sign message with submit key
submitMessageTx.Sign(myPrivateKey)
// Submit message
submitTxResponse, err := submitMessageTx.Execute(client)
if err != nil {
println(err.Error(), ": error submitting to topic")
return
}
// Get the receipt of the transaction
receipt, err := submitTxResponse.GetReceipt(client)
// Get the transaction status
transactionStatus := receipt.Status
fmt.Println("The message transaction status " + transactionStatus.String())
// Prevent the program from exiting to display the message from the mirror node to the console
time.Sleep(30000)
}
Last modified 12d ago