Build your Hedera client

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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
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-public.mirrornode.hedera.com:433 for the endpoint. The gRPC API requires TLS. The following SDK versions are compatible with TLS:
Java: v2.0.6+
JavaScript: v2.0.23+
Go: v2.1.8+
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
1
// From a pre-configured network
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Client client = Client.forTestnet();
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​
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//For a specified network
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Map<String, AccountId> nodes = new HashMap<>();
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nodes.put("34.94.106.61:50211" ,AccountId.fromString("0.0.10"));
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​
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Client.forNetwork(nodes);
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​
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//v2.0.0
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JavaScript
1
// From a pre-configured network
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const client = Client.forTestnet();
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​
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//For a specified network
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const nodes = {"35.237.200.180:50211": new AccountId(3)}
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const client = Client.forNetwork(nodes);
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​
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//v2.0.7
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Go
1
// From a pre-configured network
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client := hedera.ClientForTestnet()
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​
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//For a specified network
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node := map[string]AccountID{
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    "34.94.106.61:50211": {Account: 10}
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}
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​
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client := Client.forNetwork(nodes)
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​
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//v2.0.0
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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
Constructs 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
1
// From a pre-configured network
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Client client = Client.forTestnet();
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​
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//Replace nodes
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Map<AccountId, String> nodes = new HashMap<>();
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nodes.put(AccountId.fromString("0.0.10"), "34.94.106.61:50211" ,);
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​
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client.replaceNodes(nodes);
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​
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//v1.3.2
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JavaScript
1
// From a pre-configured network
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const client = Client.forTestnet();
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​
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//v1.4.4
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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
JavaScript
Go
1
// Operator account ID and private key from string value
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AccountId OPERATOR_ID = AccountId.fromString("0.0.96928");
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Ed25519PrivateKey OPERATOR_KEY = PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");
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​
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// Pre-configured client for test network (testnet)
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Client client = Client.forTestnet()
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​
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//Set the operator with the operator ID and operator key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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1
// Operator account ID and private key from string value
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const OPERATOR_ID = AccountId.fromString("0.0.96928");
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const OPERATOR_KEY = PrivateKey.fromString("302e020100300506032b657004220420b9c3ebac81a72aafa5490cc78111643d016d311e60869436fbb91c7330796928");
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​
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// Pre-configured client for test network (testnet)
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const client = Client.forTestnet()
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​
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//Set the operator with the operator ID and operator key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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1
// Operator account ID and private key from string value
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operatorAccountID, err := hedera.AccountIDFromString("0.0.96928")
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if err != nil {
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    panic(err)
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}
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​
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operatorKey, err := hedera.PrivateKeyFromString("302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de33596928")
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if err != nil {
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    panic(err)
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}
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​
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// Pre-configured client for test network (testnet)
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client := hedera.ClientForTestnet()
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​
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//Set the operator with the operator ID and operator key
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client.SetOperator(operatorAccountID, operatorKey)
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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
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OPERATOR_ID= 0.0.9410
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OPERATOR_KEY= 302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de3359bc5e
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Java
JavaScript
Go
1
//Grab the account ID and private key of the operator account from the .env file
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AccountId OPERATOR_ID = AccountId.fromString(Objects.requireNonNull(Dotenv.load().get("OPERATOR_ID")));
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Ed25519PrivateKey OPERATOR_KEY = Ed25519PrivateKey.fromString(Objects.requireNonNull(Dotenv.load().get("OPERATOR_KEY")));
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​
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// Pre-configured client for test network (testnet)
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Client client = Client.forTestnet()
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​
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//Set the operator with the operator ID and operator key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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1
//Grab the account ID and private key of the operator account from the .env file
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const operatorAccount = process.env.OPERATOR_ID;
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const operatorPrivateKey = process.env.OPERATOR_KEY;
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​
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// Pre-configured client for test network (testnet)
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const client = Client.forTestnet()
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​
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//Set the operator with the operator ID and operator key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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1
    err := godotenv.Load(".env")
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    if err != nil {
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        panic(fmt.Errorf("Unable to load environment variables from demo.env file. Error:\n%v\n", err))
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    }
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​
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    //Get the operator ID and operator key
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    OPERATOR_ID := os.Getenv("OPERATOR_ID")
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    OPERATOR_KEY := os.Getenv("OPERATOR_KEY")
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​
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​
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    operatorAccountID, err := hedera.AccountIDFromString(OPERATOR_ID)
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    if err != nil {
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        panic(err)
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    }
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​
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    operatorKey, err := hedera.PrivateKeyFromString(OPERATOR_KEY)
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    if err != nil {
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        panic(err)
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    }
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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
Method
Type
Description
Client.<network>.setMaxTransactionFee(<fee>)
Hbar
The maximum transaction fee the client is willing to pay. Default: 1 hbar
Client<network>.setMaxQueryPayment(<maxQueryPayment>)
Hbar
The maximum query payment the client will pay.
Default: 1 hbar
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>.setRequestTimeout(<requestTimeout>)
Duration
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>.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
Java
1
// For test network (testnet)
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Client client = Client.forTestnet()
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​
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//Set the operator and operator private key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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​
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//Set the max transaction fee the client is willing to pay to 2 hbars
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client.setMaxTransactionFee(new Hbar(2)); 
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​
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//v2.0.0
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JavaScript
1
// For test network (testnet)
2
const client = Client.forTestnet()
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​
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//Set the operator and operator private key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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​
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//Set the max transaction fee the client is willing to pay to 2 hbars
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client.setMaxTransactionFee(new Hbar(2));
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​
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//v2.0.0
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Go
1
// For test network (testnet)
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client := hedera.ClientForTestnet()
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​
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//Set the operator and operator private key
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client.SetOperator(operatorAccountID, operatorKey)
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​
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//Set the max transaction fee the client is willing to pay to 2 hbars
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client.SetMaxTransactionFee(hedera.HbarFrom(2, hedera.HbarUnits.Hbar))
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​
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//v2.0.0
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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
1
 Client client = Client.forTestnet();
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​
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 client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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​
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 client.setMaxTransactionFee(new Hbar(2));
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​
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 //v1.3.2
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JavaScript
1
// For test network (testnet)
2
const client = Client.forTestnet()
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​
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//Set the operator and operator private key
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client.setOperator(OPERATOR_ID, OPERATOR_KEY);
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​
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//Set the max transaction fee the client is willing to pay to 2 hbars
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client.setMaxTransactionFee(new Hbar(2)); 
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​
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//v1.4.4
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Documentation - Previous
SDKs
Network address book
Last modified 6d ago
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Contents
1. Configure your Hedera network
2. Define the operator account ID and private key
From an account ID and private key
From a .env file
3. Additional client modifications