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
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: v2.3.0+
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()
boolen
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 addressbook for the given network.
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
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
// 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
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
// Operator account ID and private key from string value
AccountId OPERATOR_ID = AccountId.fromString("0.0.96928");
Ed25519PrivateKey OPERATOR_KEY = PrivateKey.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);
// Operator account ID and private key from string value
const OPERATOR_ID = AccountId.fromString("0.0.96928");
const OPERATOR_KEY = PrivateKey.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);
// 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
OPERATOR_ID= 0.0.9410
OPERATOR_KEY= 302e020100300506032b65700422042012a4a4add3d885bd61d7ce5cff88c5ef2d510651add00a7f64cb90de3359bc5e
Java
JavaScript
Go
//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);
//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(operatorAccount, operatorPrivateKey );
    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 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 setDefaultMaxTransactionFee()and setDefaultMaxQueryPayment().
V2
V1
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
Limit for how many 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 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
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
Documentation - Previous
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Set-up Your Local Network
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On this page
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