Build Your Hedera Client

1. Configure your Hedera Network

Build your client to interact with any of the Hedera network nodes. Mainnet, testnet, and previewnet are the three Hedera networks you can submit transactions and queries to.

For a predefined network (preview, testnet, and mainnet), the mirror node client is configured to the corresponding network mirror node. The default mainnet mirror node connection is to the whitelisted mirror node. To access the public mainnet mirror node, use setMirrorNetwork() and enter mainnet.mirrornode.hedera.com:433 for the endpoint. The gRPC API requires TLS. The following SDK versions are compatible with TLS:

• Java: v2.3.0+

• JavaScript: v2.4.0+

• Go: v2.4.0+

Method	Type	Description
Client.forPreviewnet()		Constructs a Hedera client pre-configured for Previewnet access
Client.forTestnet()		Constructs a Hedera client pre-configured for Testnet access
Client.forMainnet()		Constructs a Hedera client pre-configured for Mainnet access
Client.forNetwork(<network>)	Map<String, AccountId>	Construct a client given a set of nodes. It is the responsibility of the caller to ensure that all nodes in the map are part of the same Hedera network. Failure to do so will result in undefined behavior.
Client.fromConfig(<json>)	String	Configure a client from the given JSON string describing a ClientConfiguration object
Client.fromConfig(<json>)	Reader	Configure a client from the given JSON reader
Client.fromConfigFile(<file>)	File	Configure a client based on a JSON file.
Client.fromConfigFile(<fileName>)	String	Configure a client based on a JSON file at the given path.
Client.forName(<name>)	String	Provide the name of the network. mainnet testnet previewnet
Client.<network>.setMirrorNetwork(<network>)	List<String>	Define a specific mirror network node(s) ip:port in string format
Client.<network>.getMirrorNetwork()	List<String>	Return the mirror network node(s) ip:port in string format
Client.setTransportSecurity()	boolean	Set if transport security should be used. If transport security is enabled all connections to nodes will use TLS, and the server's certificate hash will be compared to the hash stored in the node address book for the given network.
Client.setNetworkUpdatePeriod()	Duration	Client automatically updates the network via a mirror node query at regular intervals. You can set the interval at which the address book is updated.
Client.setNetworkFromAddressBook(<addressBook>)	AddressBook	Client can be set from a NodeAddressBook.
Client.setLedgerId(<ledgerId>)	LedgerId	The ID of the network. LedgerId.MAINNET LedgerId.TESTNET LedgerId.PREVIEWNET
Client.getLedgerId()	LedgerId	Get the ledger ID
Client.setVerifyCertificates()	boolean	Set if server certificates should be verified against an existing address book.

Java

// From a pre-configured network
Client client = Client.forTestnet();

//For a specified network
Map<String, AccountId> nodes = new HashMap<>();
nodes.put("34.94.106.61:50211" ,AccountId.fromString("0.0.10"));

Client.forNetwork(nodes);

//v2.0.0

JavaScript

// From a pre-configured network
const client = Client.forTestnet();

//For a specified network
const nodes = {"34.94.106.61:50211": new AccountId(10)}
const client = Client.forNetwork(nodes);

//v2.0.7

Go

// From a pre-configured network
client := hedera.ClientForTestnet()

//For a specified network
node := map[string]AccountID{
    "34.94.106.61:50211": {Account: 10}
}

client := Client.forNetwork(nodes)

//v2.0.0

2. Define the operator account ID and private key

The operator is the account that will, by default, pay the transaction fee for transactions and queries built with this client. The operator account ID is used to generate the default transaction ID for all transactions executed with this client. The operator private key is used to sign all transactions executed by this client.

Method	Type
Client.<network>.setOperator(<accountId, privateKey>)	AccountId, PrivateKey
Client.<network>.setOperatorWith(<accountId, privateKey, transactionSigner>)	AccountId, PrivateKey, Function<byte[ ], byte [ ]>

From an account ID and private key

Java

// Operator account ID and private key from string value
AccountId MY_ACCOUNT_ID = AccountId.fromString("0.0.96928");
Ed25519PrivateKey MY_PRIVATE_KEY = PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");

// Pre-configured client for test network (testnet)
Client client = Client.forTestnet()

//Set the operator with the account ID and private key
client.setOperator(MY_ACCOUNT_ID, MY_PRIVATE_KEY);

JavaScript

// Your account ID and private key from string value
const MY_ACCOUNT_ID = AccountId.fromString("0.0.96928");
const MY_PRIVATE_KEY = PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");

// Pre-configured client for test network (testnet)
const client = Client.forTestnet()

//Set the operator with the account ID and private key
client.setOperator(MY_ACCOUNT_ID, MY_PRIVATE_KEY);

Go

// Operator account ID and private key from string value
operatorAccountID, err := hedera.AccountIDFromString("0.0.96928")
if err != nil {
    panic(err)
}

operatorKey, err := hedera.PrivateKeyFromString("302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de33596928")
if err != nil {
    panic(err)
}

// Pre-configured client for test network (testnet)
client := hedera.ClientForTestnet()

//Set the operator with the operator ID and operator key
client.SetOperator(operatorAccountID, operatorKey)

From a .env file

The .env file is created in the root directory of the SDK. The .env file stores account ID and the associated private key information to reference throughout your code. You will need to import the relevant dotenv module to your project files. The sample .env file may look something like this:

.env

MY_ACCOUNT_ID=0.0.941
MY_PRIVATE_KEY=302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de3359bc5e

Java

//Grab the account ID and private key of the operator account from the .env file
AccountId MY_ACCOUNT_ID = AccountId.fromString(Objects.requireNonNull(Dotenv.load().get("OPERATOR_ID")));
Ed25519PrivateKey MY_PRIVATE_KEY = Ed25519PrivateKey.fromString(Objects.requireNonNull(Dotenv.load().get("OPERATOR_KEY")));

// Pre-configured client for test network (testnet)
Client client = Client.forTestnet()

//Set the operator with the account ID and private key
client.setOperator(MY_ACCOUNT_ID, MY_PRIVATE_KEY);

JavaScript

//Grab the account ID and private key of the operator account from the .env file
const myAccountId = process.env.MY_ACCOUNT_ID;
const myPrivateKey = process.env.MY_PRIVATE_KEY;

// Pre-configured client for test network (testnet)
const client = Client.forTestnet()

//Set the operator with the account ID and private key
client.setOperator(myAccountId, myPrivateKey);

Go

    err := godotenv.Load(".env")
    if err != nil {
        panic(fmt.Errorf("Unable to load environment variables from demo.env file. Error:\n%v\n", err))
    }

    //Get the operator account ID and private key
    MY_ACCOUNT_ID := os.Getenv("MY_ACCOUNT_ID")
    MY_PRIVATE_KEY := os.Getenv("MY_PRIVATE_KEY")


    myAccountID, err := hedera.AccountIDFromString(MY_ACCOUNT_ID)
    if err != nil {
        panic(err)
    }

    myPrivateKey, err := hedera.PrivateKeyFromString(MY_PRIVATE_KEY)
    if err != nil {
        panic(err)
    }

3. Additional client modifications

The max transaction fee and max query payment are both set to 100_000_000 tinybar (1 HBAR). This amount can be modified by using setDefaultMaxTransactionFee()and setDefaultMaxQueryPayment().

Method	Type	Description
Client.<network>.SetDefaultRegenerateTransactionId(<regenerateTransactionId>)	boolean	Whether or not to regenerate the transaction IDs
Client.<network>.getDefaultRegenerateTransactionId(<regenerateTransactionId>)	boolean	Get the default regenerate transaction ID boolean value
Client.<network>.setDefaultMaxTransactionFee(<fee>)	Hbar	The maximum transaction fee the client is willing to pay
Client.<network>.getDefaultMaxTransactionFee()	Hbar	Get the default max transaction fee that is set
Client<network>.setDefaultMaxQueryPayment(<maxQueryPayment>)	Hbar	The maximum query payment the client will pay. Default: 1 hbar
Client<network>.getDefaultMaxQueryPayment()	Hbar	Get the default max query payment
Client.<network>.setNetwork(<nodes>)	Map<String, AccountId>	Replace all nodes in this Client with a new set of nodes (e.g. for an Address Book update)
Client.<network>.getNetwork()	Map<String, AccountId>	Get the network nodes
Client.<network>.setRequestTimeout(<requestTimeout>)	Duration	The period of time a transaction or query request will retry from a "busy" network response
Client.<network>.getRequestTimeout()	Duration	Get the period of time a transaction or query request will retry from a "busy" network response
Client.<network>.setMinBackoff(<minBackoff>)	Duration	The minimum amount of time to wait between retries. When retrying, the delay will start at this time and increase exponentially until it reaches the maxBackoff
Client.<network>.getMinBackoff()	Duration	Get the minimum amount of time to wait between retries
Client.<network>.setMaxBackoff(<maxBackoff>)	Duration	The maximum amount of time to wait between retries. Every retry attempt will increase the wait time exponentially until it reaches this time.
Client.<network>.getMaxBackoff()	Duration	Get the maximum amount of time to wait between retries
Client.<network>.setAutoValidateChecksums(<value>)	boolean	Validate checksums
Client.<network>.setCloseTimeout(<closeTimeout>)	Duration	Timeout for closing either a single node when setting a new network, or closing the entire network
Client.<network>.setMaxNodeAttempts(<nodeAttempts>)	int	Set the max number of times a node can return a bad gRPC status before we remove it from the list
Client.<network>.getMaxNodeAttempts()	int	Get the max node attempts set
Client.<network>.setMinNodeReadmitTime(<readmitTime>)	Duration	The min time to wait before attempting to readmit nodes
Client.<network>.getMinNodeReadmitTime()	Duration	Get the minimum node readmit time
Client.<network>.setMaxNodeReadmitTime(<readmitTime>)	Duration	The max time to wait before attempting to readmit nodes
Client.<network>.getMaxNodeReadmitTime()	Duration	Get the max node readmit time

Java

// For test network (testnet)
Client client = Client.forTestnet()

//Set your account as the client's operator
client.setOperator(myAccountId, myPrivateKey);

//Set the default maximum transaction fee (in Hbar)
client.setDefaultMaxTransactionFee(new Hbar(10));

//Set the maximum payment for queries (in Hbar)
client.setDefaultMaxQueryPayment(new Hbar(5));

//v2.0.0

JavaScript

JavaScript

// For test network (testnet)
const client = Client.forTestnet()

//Set your account as the client's operator
client.setOperator(myAccountId, myPrivateKey);

//Set the default maximum transaction fee (in Hbar)
client.setDefaultMaxTransactionFee(new Hbar(10));

//Set the maximum payment for queries (in Hbar)
client.setDefaultMaxQueryPayment(new Hbar(5));

//v2.0.0

Go

// For test network (testnet)
client := hedera.ClientForTestnet()

//Set your account as the client's operator
client.SetOperator(myAccountId, myPrivateKey)

// Set default max transaction fee
client.SetDefaultMaxTransactionFee(hedera.HbarFrom(10, hedera.HbarUnits.Hbar))

// Set max query payment
client.setDefaultMaxQueryPayment(hedera.HbarFrom(5, hedera.HbarUnits.Hbar))

//v2.0.0