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.

V2
V1
V2

For a predefined network (preview, testnet, and mainnet), the mirror node client is configured to the corresponding network mirror node.

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.fromJson(<json>)

String

Configure a client from the given JSON string

Client.fromJson(<json>)

Reader

Configure a client from the given JSON reader

Client.fromJsonFile(<file>)

File

Configure a client based on a JSON file.

Client.fromJsonFile(<fileName>)

String

Configure a client based on a JSON file at the given path.

Client.<network>.setMirrorNetwork(network)

List<String>)

Define a specific mirror network node(s) ip:port in string format

Java
// From a pre-configured network
Client client = Client.forTestnet();
//For a specified node(s)
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();
Go
// From a pre-configured network
client := hedera.ClientForTestnet()
//From a specifed node(s)
node := map[string]AccountID{
"34.94.106.61:50211": {Account: 10}
}
client := Client.forNetwork(nodes)
//v2.0.0
V1

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.fromFile(<file>)

File

Configures a client from a file

Client.fromFile(<fileName>)

String

Contructs a network from a file

Client.fromJson(<json>)

String

Configure a client from the given JSON string

Client.fromJson(<json>)

Reader

Configure a client from the given JSON reader

Client.replaceNodes(<nodes>)

Map<AccountId, String>

Replaces nodes in the network

Java
// From a pre-configured network
Client client = Client.forTestnet();
//Replace nodes
Map<AccountId, String> nodes = new HashMap<>();
nodes.put(AccountId.fromString("0.0.10"), "34.94.106.61:50211" ,);
client.replaceNodes(nodes);
//v1.3.2
JavaScript
// From a pre-configured network
const client = Client.forTestnet();
//v1.4.4

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

setOperator(<accountId, privateKey>)

AccountId, PrivateKey

setOperatorWith(<accountId, privateKey, transactionSigner>)

AccountId, PrivateKey, Function<byte[ ], byte [ ]>

From an account ID and private key

Java
JavaScript
Go
Java
// Operator account ID and private key from string value
AccountId OPERATOR_ID = AccountId.fromString("0.0.96928");
Ed25519PrivateKey OPERATOR_KEY = Ed25519PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");
// Pre-configured client for test network (testnet)
Client client = Client.forTestnet()
//Set the operator with the operator ID and operator key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
JavaScript
// Operator account ID and private key from string value
const OPERATOR_ID = AccountId.fromString("0.0.96928");
const OPERATOR_KEY = Ed25519PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");
// Pre-configured client for test network (testnet)
const client = Client.forTestnet()
//Set the operator with the operator ID and operator key
client.setOperator(OPERATOR_ID, OPERATOR_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 relevent dotenv module to your project files. The sample .env file may look something like this:

.env
OPERATOR_ID= 0.0.9410
OPERATOR_KEY= 302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de3359bc5e
Java
JavaScript
Go
Java
//Grab the account ID and private key of the operator account from the .env file
AccountId OPERATOR_ID = AccountId.fromString(Objects.requireNonNull(Dotenv.load().get("OPERATOR_ID")));
Ed25519PrivateKey OPERATOR_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 operator ID and operator key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
JavaScript
//Grab the account ID and private key of the operator account from the .env file
const operatorAccount = process.env.OPERATOR_ID;
const operatorPrivateKey = process.env.OPERATOR_KEY;
// Pre-configured client for test network (testnet)
const client = Client.forTestnet()
//Set the operator with the operator ID and operator key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
Go
err := godotenv.Load(".env")
if err != nil {
panic(fmt.Errorf("Unable to load enviroment variables from demo.env file. Error:\n%v\n", err))
}
//Get the operator ID and operator key
OPERATOR_ID := os.Getenv("OPERATOR_ID")
OPERATOR_KEY := os.Getenv("OPERATOR_KEY")
operatorAccountID, err := hedera.AccountIDFromString(OPERATOR_ID)
if err != nil {
panic(err)
}
operatorKey, err := hedera.PrivateKeyFromString(OPERATOR_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 setMaxTransactionFee()and setMaxQueryPayment().

V2
V1
V2

Method

Type

Description

setMaxTransactionFee(<fee>)

Hbar

The maximum transaction fee the client is willing to pay. Default: 1 hbar

setMaxQueryPayment(<maxQueryPayment>)

Hbar

The maximum query payment the client will pay.

Default: 1 hbar

setNetwork(<nodes>)

Map<String, AccountId>

Replace all nodes in this Client with a new set of nodes (e.g. for an Address Book update)

setRequestTimeout(<requestTimeout>)

Duration

The period of time a transaction or query request will retry from a "busy" network response

Java
// For test network (testnet)
Client client = Client.forTestnet()
//Set the operator and operator private key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
//Set the max transaction fee the client is willing to pay to 2 hbars
client.setMaxTransactionFee(new Hbar(2));
//v2.0.0
JavaScript
// For test network (testnet)
const client = Client.forTestnet()
//Set the operator and operator private key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
//Set the max transaction fee the client is willing to pay to 2 hbars
client.setMaxTransactionFee(new Hbar(2));
//v2.0.0
Go
// For test network (testnet)
client := hedera.ClientForTestnet()
//Set the operator and operator private key
client.SetOperator(operatorAccountID, operatorKey)
//Set the max transaction fee the client is willing to pay to 2 hbars
client.SetMaxTransactionFee(hedera.HbarFrom(2, hedera.HbarUnits.Hbar))
//v2.0.0
V1

Method

Type

Description

setMaxTransactionFee(<fee>)

Hbar/long

The maximum transaction fee the client is willing to pay. Default: 1 hbar

setMaxQueryPayment(<maxQueryPayment>)

Hbar/long

The maximum query payment the client will pay.

Default: 1 hbar

Java
Client client = Client.forTestnet();
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
client.setMaxTransactionFee(new Hbar(2));
//v1.3.2
JavaScript
// For test network (testnet)
const client = Client.forTestnet()
//Set the operator and operator private key
client.setOperator(OPERATOR_ID, OPERATOR_KEY);
//Set the max transaction fee the client is willing to pay to 2 hbars
client.setMaxTransactionFee(new Hbar(2));
//v1.4.4